DRAFT REPORT FOR CONSULTATION: DO NOT REFERENCE

1
2
3
4

5
6
7
8
9

ICRP ref: 4854-2345-7344

Annals of the ICRPICRP PUBLICATION 15X

10
11
12
13

Practical Aspects in Optimisation of RadiologicalProtection in Digital Radiography, Fluoroscopy, and CT

14
15
16
17
18
19
20
21
22
23
24
25
26
27
28

Editor-in-Chief

C.H. CLEMENT
Associate Editor

T. YASUMUNE
Authors on behalf of ICRP
C. J. Martin, K. Applegate, J. Damilakis, I. Hernandez-Giron, M. Kortesniemi,
H. Khoury, K.H. Ng, D. Pekarovic, D.G. Sutton, J. Vassileva

29

PUBLISHED FOR

30

The International Commission on Radiological Protection

31
32

by

33
34
35
36

Please cite this issue as ‘ICRP, 20xx. Title of the issue. ICRP Publication 15X. Ann.
ICRP xx(x).’1

DRAFT REPORT FOR CONSULTATION: DO NOT REFERENCE

37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71

CONTENTSABSTRACT ........................................................................................................................... 04
MAIN POINTS ...................................................................................................................... 06
1. INTRODUCTION .............................................................................................................. 07
1.1. Background ................................................................................................................. 07
1.2. Practical techniques for optimisation in digital radiology ........................................... 09
1.3. The role of AI in optimisation ..................................................................................... 10
1.4. Previous ICRP publications on digital radiology ......................................................... 11
2. DIGITAL RADIOGRAPHY .............................................................................................. 13
2.1. The digital radiography system .................................................................................... 13
2.2. Optimisation of exposure factors and radiation quality ................................................ 15
2.3. Other aspects of optimisation ....................................................................................... 222.4. Factors to consider in optimisation .............................................................................. 26
2.5. Image post processing .................................................................................................. 28
2.6. Optimisation of the imaging workflow......................................................................... 29
2.7. Basic quality assurance (QA) ....................................................................................... 30
2.8. Approaches to Optimisation ........................................................................................ 32
3. INTERVENTIONAL AND OTHER FLUOROSCOPIC PROCEDURES ......................... 34
3.1. The evolution of fluoroscopic techniques .................................................................... 34
3.2. Design features of modern fluoroscopy systems relevant to patient dose and image
quality .......................................................................................................................... 36
3.3. Exposure configuration and optimisation during commissioning ................................ 39
3.4. Establishing equipment performance and QC programme ........................................... 42
3.5. Patient dose monitoring and dose audits ...................................................................... 43
3.6. Skin dose monitoring and alert levels ........................................................................... 44
3.7. Practical advice for optimal performance of fluoroscopy procedures and patientmanagement ................................................................................................................ 46
3.8. Dose management QA programme .............................................................................. 52
4. MULTI-DETECTOR COMPUTED TOMOGRAPHY ...................................................... 55
4.1. The increasing use of computed tomography ............................................................... 55
4.2. The CT image .............................................................................................................. 57
4.3. Image reconstruction ................................................................................................... 62
4.4. Automatic tube current modulation (ATCM) ............................................................... 64
4.5. Other CT technologies and procedures ........................................................................ 68
4.6. Development of clinical CT protocols ......................................................................... 72

72
73
74
75
76
77
78
79

5. PAEDIATRIC PROCEDURES .......................................................................................... 83

80

5.1. Requirements for imaging paediatric patients .............................................................. 832

DRAFT REPORT FOR CONSULTATION: DO NOT REFERENCE

81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113

5.2. Adjustments in image quality requirements and dose with patient size ....................... 88
5.3. Development of optimisation for paediatric imaging ................................................... 98
6. EXAMINATIONS OF PREGNANT PATIENTS ............................................................. 100
6.1. Introduction ............................................................................................................... 100
6.2. Performance of x-ray procedures on pregnant patient ................................................ 101
6.3. Methods to estimate conceptus dose .......................................................................... 102
6.4. Pregnancy screening before radiologic examinations ................................................ 103
6.5. Protective shielding of the conceptus ......................................................................... 103
6.6. Optimisation of x-ray procedures for pregnant patients ............................................. 104
7. CONCLUSIONS .............................................................................................................. 109
REFERENCES ..................................................................................................................... 111
ANNEX A. DOSE QUANTITIES AND UNITS .................................................................. 126
A.1. References ................................................................................................................ 126
ANNEX B. AUTOMATED SYSTEMS FOR RADIATION EXPOSURE
MONITORING..................................................................................................................... 127
B.1. Digital Imaging and Communication in Medicine (DICOM) .................................... 127
B.2. Radiation Dose Structured Report (RDSR) ............................................................... 127
B.3. Picture archiving and communication system (PACS) .............................................. 128
B.4. Radiology information system (RIS) ........................................................................ 128
B.5. The RadLex Playbook ............................................................................................... 128
B.6. References ................................................................................................................. 129
ABBREVIATIONS .............................................................................................................. 130
GLOSSARY ......................................................................................................................... 134
ACKNOWLEDGEMENTS ................................................................................................. 138

3

DRAFT REPORT FOR CONSULTATION: DO NOT REFERENCEICRP Publication 15X
114
115

PRACTICAL ASPECTS IN OPTIMISATION OF RADIOLOGICALPROTECTION FOR DIGITAL RADIOGRAPHY, FLUOROSCOPY, AND CT

116

ICRP PUBLICATION 15X

117

Approved by the Commission in Month 20YY

118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151

Abstract Digital radiology is playing an increasingly important role in medicine world-wide.
The use of computed tomography (CT) has risen dramatically in recent decades and makes up
about half of the population dose from medical exposures in many parts of the world. In
addition, ever more complex interventional procedures guided by fluoroscopy are replacing
more invasive surgical techniques, thus substituting risks from surgery with lesser ones fromradiation. These radiological techniques provide significant health benefits, but the associatedradiation dose levels need to be kept commensurate with the benefit accrued. Key factors inachieving this are ensuring that examinations are only carried out when they can contribute to
management of a patient’s condition and that the radiological protection aspects for all
exposures are optimised. The latter is the subject of the present publication. Digital imaging
data contribute versatility in image acquisition, post-processing, and presentation, and provide
opportunities for optimisation. However, unlike their analogue equivalent, images acquired
digitally may not provide an indication that a dose is too high or images are not collimated, so
there are new problems that have to be addressed. In Publication 15x (ICRP, 2022), threefundamental requirements for taking the optimisation process forward were described. Theseare 1) the need for collaboration between radiologists and other physicians, radiographers,
medical physicists and managers, 2) access to the appropriate methodology, technology andexpertise, and 3) provision of organisational processes that ensure tasks, such as equipment
performance tests, patient dose surveys and reviews of protocols are carried out. A high-level
requirement is the integration and use of decision sciences, and harmonisation of these
optimisation processes across multispecialty clinical teams and equipment types within
healthcare systems. This publication contains information on practical methods needed to carry
optimisation forward for different imaging techniques; radiography, fluoroscopy (andfluoroscopically guided interventional procedures) and CT. Many features of digitalequipment allow dose levels to be reduced while still maintaining adequate image quality forthe clinical task. Staff need to understand the relationship between the different selectableoptions to use the features effectively. However, there is a wide range in available equipment
and training around the world. Provision ranges from clinics with simple radiographic units tospecialist hospitals with complex state-of-the-art equipment. Some countries have establishedcommunities of medical physicists, while in others there is little or no medical physics support.
This presents challenges in communicating requirements for optimisation. This document
addresses these challenges by providing information for facilities, within broad categories
linked to optimisation arrangements already in place, D: Preliminary, C: Basic, B:
Intermediate, and A: Advanced (ICRP, 2022). It is hoped that through this approach, radiology

4

DRAFT REPORT FOR CONSULTATION: DO NOT REFERENCE

152
153

teams will be able to plan strategies for introducing optimisation techniques that are appropriate
for their own facilities and equipment.

154© 20YY ICRP. Published by SAGE.

155

Keywords: Digital radiography, Fluoroscopy, Fluoroscopically guided interventions,
Computed tomography, Optimisation, Paediatric radiology, Pregnant patients

156

5

DRAFT REPORT FOR CONSULTATION: DO NOT REFERENCE

MAIN POINTS

157
158
159
160
161
162

•

Optimisation of radiological protection in diagnostic imaging and image-guided
procedures should be built on collaboration between radiologists, radiographersand medical physicists and developed from the initial level D when a facility is set
up, to the basic requirements of optimisation level C, through the intermediate level
B, to advanced processes of optimisation level A, as set out in this report.

163
164
165
166

•

Exposure factors for digital radiography should be established for different
anatomical regions and patient characteristics, making use of automatic exposure
control devices and possible use of copper filtration, especially for paediatric
exposures, and exposure indices and image collimation monitored.

167
168
169
170

•

Exposure factor selection programmes for fluoroscopy should be configured toprovide the diagnostic information required for the range of clinical tasks at
commissioning, and dose and image quality performance monitored throughregular quality control.

171
172
173
174
175

•

Development of protocols for CT to give a level of image quality that has been
agreed among the professionals involved, requires consideration of theinterdependence of exposure parameters, proper application of automatic tube
current modulation, and iterative or deep-learning based reconstruction to enable
lower dose settings to be used.

176
177
178
179
180

•

Paediatric protocol optimisation requires an understanding of clinical indications,patient sizes, and the ability of patients to cooperate and, as for all interventional
procedures, occupational protection should be managed in an integrated mannerwith patient protection. Protocols for pregnant patients require optimisation to
reduce doses for both mother and conceptus.

6

DRAFT REPORT FOR CONSULTATION: DO NOT REFERENCE

1. INTRODUCTION

181

182

1.1. Background

183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226

(1) The principle of optimisation has been a major part of radiological protection thinking
for three decades (ICRP, 1991) and is key to effective use of medical imaging. Optimisation in
relation to medical imaging requires provision of clinical images for individual patients thatare of sufficient quality to ensure accurate and reliable diagnoses, in order to enable correctcare decisions to be made. In addition, the radiation doses used in acquiring such clinicalimages should be adjusted so that, while being adequate to produce the images, they areminimised to the level appropriate to the applied imaging technology. This publication deals
with the practical aspects of optimisation relating to the different digital radiology modalities.
(2) Publication 73 identified two areas in which optimisation of protection should beapplied in medicine, i) the design and construction of equipment and installations, and ii) the
day-to-day methods of working (ICRP, 1996). Optimisation is not a single action and there aremany aspects that need to be in place before an x-ray facility can even embark on the road toachieving optimisation; these are not straight forward and have become quite complex in thehealthcare environment. Proper initial education and ongoing training of staff on operation ofequipment is crucial to starting the process (Vassileva et al., 2022). However, this needs to becoupled with arrangements for the ongoing monitoring, review, and analysis of imaging
performance, that can be used to gradually improve overall effectiveness (ICRP, 2022).
Optimisation of medical imaging involves continuing improvement with the development ofknowledge, skills, competencies, and experience.
(3) Publication 15x sets out three building blocks on which strategies for achieving
optimisation should be built (ICRP, 2022). The cornerstone is professionalism; namely
collaboration between professionals, with radiologists, radiographers and medical physicists
working together as a team within an organisation that provides a structure to facilitate theprocess. The radiologist can judge whether the image quality is sufficient for the diagnostic
purpose, the radiographer should know the practical operation and limitations of the equipment,
and the medical physicist should understand the physical principles behind image formation
and be able to perform and interpret measurements of dose and image quality. The clinician,radiologist, and radiographer work together to understand the ability of the patient to undergo
an imaging examination. The increasing technical and computational complexity in radiology
equipment and applications underlines the importance of this multi-professional collaborationand dependency on the combined knowledge of different professionals.
(4) The second building block is concerned with methodology. It encompasses theknowledge and skills required in combination with the instruments and test objects needed toevaluate the performance of imaging equipment. Digital imaging carries the potential forimages to be obtained with a wide range of exposures, enabling levels to be adapted to thediagnostic requirements of particular examinations. Moreover, new features and techniquesthat can improve image quality and potentially enable clinical images to be obtained with lower
patient doses are becoming available all the time. Almost inevitably these features introduce
additional complexities. If they are not deployed effectively, because of limited awareness of
their mode of operation, the doses received by patients may be far from optimal.
(5) The third building block is concerned with processes. The requirement to put in place
processes to manage the activities that ensure a quality assurance programme is established inorder to maintain performance. An example would be the audit of patient doses against local,
national or regional diagnostic reference levels (DRLs) (ICRP, 2017). Results should be
7

DRAFT REPORT FOR CONSULTATION: DO NOT REFERENCE

227
228
229
230
231

combined with clinical assessments to feed into the development of examination protocols thatare optimised for the clinical purpose. The management systems should confirm thatmeasurements and assessments are made, that protocols are reviewed regularly and that allavailable data from clinical use and performance measurements are used in making adjustments
to protocols and to identify areas for practice improvement.

232
233
234
235
236
237
238
239
240
241

Fig.1.1. The three main components in the development and maturation of optimisation;
processes, methodology and professionalism. The levels represent different stages inachievement moving upwards from D, through B, and C, towards A. Level D represents a basic
infrastructural level as a prerequisite for initiation of the optimisation process. A, B, and C set
out the arrangements that will be in place for each component when that level is achieved. The
lower section shows the stage after the adoption of DRLs (whether local, national or regional)
has occurred. Processes are in place to require both regular quality control (QC) tests and dose
audit against the DRLs, and use of the information obtained in optimising protocols andproviding feedback, indicated by the arrows.

242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257

(6) There are large variations in the levels of knowledge, skills and competencies (KSCs),
and the availability of radiology professionals between different clinics, hospitals, andcountries. There is also a wide range in available equipment, resources, and expertise aroundthe world. Radiology service provision ranges from clinics in remote locations with simple
radiographic units to specialist hospitals with multiple computed tomography (CT) scanners
and interventional units. In some countries there are established communities of medical
physicists, while in others medical physics support is in short supply or even non-existent, andfunding to expand this may be limited. The range in available resources presents significant
challenges when communicating a harmonised route through the various steps in the
optimisation process, since facilities will be at different stages in the process and have different
arrangements in place. Therefore, priorities for appropriate action will depend on what shouldbe the next stage in their development.
(7) This document attempts to address those challenges by providing detail for facilities,
within broad categories for levels of optimisation, divided into D: Preliminary (before actions
have been taken to start the process of optimisation); C: Basic; B: Intermediate; and A:
Advanced, as described in Publication 15x (Fig. 1.1). Advice and training from experts through8

DRAFT REPORT FOR CONSULTATION: DO NOT REFERENCE

258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287

the International Atomic Energy Agency and other international organisations is alreadyproviding assistance in putting building blocks in place in nations, where optimisation is at
levels D and C. Sometimes achievement of specific aims, such as the setting of national DRLs
can become the main goal when a country starts to consider requirements for optimisation, andthis can obscure the long-term objectives. Publication 15x attempts to set out guidance to assist
in the review of arrangements that are in place in different departments so that strategies canbe developed to assess requirements for the next stage in optimisation. Such strategies can beused in planning arrangements for developing an optimisation programme that will be carriedforward into the future.
(8) There will be continual development in equipment and software technologies and thenecessary KSCs of the radiology professionals that should feed into a process of steady
improvement. Career-long commitment to training should be ensured through government
and/or employer resources, accreditation of educational programmes, and standard initial andperiodic competency assessments (ICRP, 2009; Vassileva et al., 2022). Optimisation is not a
static process to be ignored and forgotten once a particular goal has been achieved; it requires
constant attention with frequent monitoring of performance, feedback of experience, andregular review to provide continual refinement of the service to the patient (ICRP, 2006).
(9) Before going on to discuss optimisation in the context of digital radiology in more detail,something should be said about the appropriateness of the term ‘ALARA’ (as low as reasonably
achievable) that is used in relation to optimisation of protection for occupational and public
exposure situations. The term is not appropriate when referring to medical uses of radiation as
it omits an important component, namely the benefit that is derived by the patient from theexposure. As stated in Publication 120 ‘the entire concept [of optimisation applied to medical
exposures] implies keeping patient exposure to the minimum necessary to achieve the required
medical objective (diagnostic or therapeutic) (ICRP, 2013a). In diagnostic imaging and x-rayguided interventions, it means that the number and quality of images are adequate to obtain theinformation needed for diagnosis or intervention (Samei et al., 2018). In radiation therapy, thedose to normal tissue should be kept as low as possible, within the conditions required toachieve the therapeutic objective. Use of the abbreviation ‘ALARA’ alone and out of thiscontext may be misleading and raise unnecessary controversy.

288

1.2 . Practical techniques for optimisation in digital radiology

289
290
291
292
293
294
295
296
297
298
299
300
301
302
303

(10) Technological innovations that have the potential to provide a higher degree of
optimisation are being implemented continually. When new software is added to existing
equipment, it is essential that adequate training be provided to end users. This training typicallyis provided by the vendor application specialist but the medical physicist and radiographer
supervisors may also contribute to local training. Assessments of aspects of image quality as
well as radiation dose are now used in controlling exposure levels, increasing the importanceof combined parameter settings for optimisation. As the level of sophistication develops, thevariety and complexity of procedures that are possible increases. To make full use of newfeatures, the performance of equipment needs to be monitored and analysed, and examination
protocols refined as more experience is gained.
(11) Operation of all digital radiology imaging involves the need to understand theinterdependence of patient dose and image quality. This publication will not deal with these
aspects in detail except where they relate to performance of a particular type of equipment.
Instead, readers are directed to Publication 15x that contains sections dealing in more depthwith considerations of equipment installation and life cycle, dose audit and image quality
9DRAFT REPORT FOR CONSULTATION: DO NOT REFERENCE

304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336

analysis (ICRP, 2022), and to Publication 135 in relation to the setting and use of DRLs (ICRP,
2017).
(12) As technology develops, sophisticated imaging equipment (such as CT scanners) is
being acquired in countries where there may not be the degree of professional expertiseavailable that potentially exists in nations where such equipment has been available for someyears. Paying full attention to both the proper training of staff and the provision of instructions
on techniques for optimisation linked to new equipment is therefore becoming ever more
important. The present publication provides guidance on techniques for optimisation linked todifferent imaging modalities in digital radiology. It identifies components that will be importantfor facilities implementing optimisation, as they move up the levels referred to above, from D
to C – Basic, B – Intermediate, and A - Advanced. The stage of optimisation that different
facilities have achieved will depend on the numbers of staff available, their training andexperience, and the equipment available. In order to assist in the identification of thearrangements for optimisation that facilities at different levels might be expected to have andthose they need to develop, a Box is included at the end of each modality chapter listing thearrangements that should be in place at the different levels. Facility staff and managers should
use these lists as a guide to evaluate departments and identify aspects that it would beappropriate to focus on for their next stage of development.
(13) The publication is aimed at radiologists, interventional proceduralists, radiographers,
medical physicists, vendors, and radiology management. Parts are also intended for use byother clinicians, relevant expert societies/organisations and regulators. There will be parts thatare more suitable for one group or another group. For example, in Section 2 on radiography,
some parts deal with optimisation as part of the day-to-day work of the radiographer. On theother hand, there are parts of Sections 2, 3, and 4 that deal with aspects of equipment
performance set up during commissioning, which are of most relevance to medical physicists,
but that need to be taken forward in discussion with radiologists and radiographers. There arealso approaches for interventional procedures in Section 3, which will be of prime interest toradiologists and other clinicians performing them, but of relevance to other groups. Facility
managers and regulators should understand the optimisation processes for different populations
and clinical needs. Moreover, they should understand the need for adequate and sufficiently
trained human resources as a prerequisite for putting a successful optimisation process in place.
Indeed, without enough working hands and minds, the practical optimisation undertaken will
inevitably remain at a superficial level.

337

1.3. The role of AI in optimisation

338
339
340
341
342
343
344
345
346
347
348
349

(14) Interest in artificial intelligence (AI) as a way of improving the value of medical images
in early diagnosis and optimising patient management is the focus of many research studies atthe present time (Ranschaert et al., 2019; ICRP, 2022). However, there are many technical,
legal and ethical challenges to be solved before it can become a robust tool that can be widelyadopted in clinical practice (Sahiner et al., 2019). Machine learning (ML) is a form of AI
methodology, involving the development of computer programmes that can find complex
patterns, which might represent lesions or other features, within complex data sets. ML has
been developed to learn from data without being explicitly programmed. A model ormathematical algorithm is trained on image data sets to enable it to predict an outcome for new
patient data similar to that given by a human expert.
(15) Deep learning (DL) is a subset of ML and applies deep neural networks (Suzuki et al.,2017; Esteva et al., 2019). DL has become feasible in the last decade due to the enormous
10DRAFT REPORT FOR CONSULTATION: DO NOT REFERENCE

350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371

number of medical images and other big data now being produced and advancements incomputer hardware and graphics processing. To be successful DL typically (in supervised
learning) requires massive annotated datasets for DL model training, validation and testing.
The DL methods, are already yielding promising results in medical imaging related to many
diagnostic tasks, such as lesion or tissue localisation, segmentation, classification andprediction of clinical outcomes and are being used in CT image reconstruction.
(16) AI methods can enable reductions in patient dose through automation and optimisationof data acquisition processes, including patient positioning and acquisition parameter settings(McCullough and Leng, 2019) and optimisation of the radiological chain. Image quality
measurement, classification and grading, in addition to patient specific dosimetry, may beachieved using a ML/DL approach and ultimately replace traditional methods such as modelobservers for image quality assessment and Monte Carlo simulations for dosimetry calculations(Samei and Kruipinski, 2018, Inkinen at al., 2022). Although digital radiology is potentiallywell suited to DL, its application in diagnosis requires high quality, high volume, image andoutcome data, and the number of potential clinical scenarios is huge. A major challenge is inaccess to sufficient annotated (if supervised learning is applied) and representative training data,
which is a fundamental prerequisite if sufficient robustness is to be achieved in making AI
methods more generally applicable and properly validated to the clinical setting. This will
require not only regulatory approval of algorithms and procedures, but measures in hospitals
to ensure the methods are appropriate for local patient cohorts. AI will be an elemental part ofradiological imaging in the future, although it will take time to reach clinical implementationand integration from the research and development projects.

372

1.4. Previous and upcoming ICRP publications on digital radiology

373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395

(17) In the last two decades, ICRP has prepared publications focussing on the technicalrequirements for optimisation with regard to the various modalities using ionising radiology,
namely radiography, fluoroscopy, and CT. These documents have provided practicalmethodologies for optimisation to address the needs arising from the development of newtechnologies.
(18) Digital radiography enabled the image data to be processed to give images optimisedfor viewing, but made high (and low) exposures more difficult to identify. ICRP prepared areport to facilitate the transition from film/screen to digital radiography (ICRP, 2004). Section
2 of this report will extend the advice given and deal with the pitfalls in optimisation during
routine use of digital radiography.
(19) In the meantime, the rapid development of fluoroscopically guided interventions had
led to the appearance of cases of tissue reactions in patients in radiological imaging. A reporton guidance to avoid radiation injuries was published to address this risk (ICRP, 2000b). Other
publications have since followed to provide guidance following developments in the use offluoroscopically guided procedures by other specialties outside the imaging department (ICRP,
2010) and the increased use of imaging in cardiology (ICRP, 2013a). Section 3 will augment
the measures described for general optimisation of patients’ exposures in these reports, but will
not deal with the risk of tissue reactions to the same depth. ICRP recently provided a detailed
report on occupational radiological protection for interventional procedures (ICRP, 2018a) so
this report will not deal with occupational exposure issues in any depth, but emphasises thatoccupational protection should be managed in an integrated approach with patient protection.
(20) ICRP has two publications that cover optimisation in terms of managing patient dosein conventional CT, for single slice and multi-slice CT (ICRP, 2000c, 2007a). However, there
11

DRAFT REPORT FOR CONSULTATION: DO NOT REFERENCE

396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426

has since been a huge development in CT hardware and software such as iterative
reconstruction that were not discussed in the earlier publications, and others such as automatictube current modulation for which the software has evolved since the previous publication.
There will be extensive discussion of opportunities for optimisation in CT in Section 4, as wellas risks of higher dose levels if potential dose reduction features are not fully understood and/or
used incorrectly. In addition, ICRP has published a report on cone beam CT (ICRP, 2015), but
discussion in this document is confined to the application of cone beam on C-arm fluoroscopic
and interventional units. ICRP Task Group 117 will provide a report on CT optimisation whenused with positron emission tomography (PET) and single photon emission tomography(SPECT) in hybrid imaging (ICRP, TG117).
(21) The specific needs and challenges in diagnostic and interventional procedures of
paediatric patients, for whom the risks of radiation exposure are greater, were addressed in
ICRP (2013b). The optimisation methods for paediatric imaging will be developed further in
Section 5. ICRP set out the approach to medical exposures on pregnant patients in Publication
84 (ICRP, 2000a) to take account of the higher risk of childhood leukaemia resulting from fetal
exposures. Section 6 considers the approach to optimisation of exposures during pregnancy interms of minimising the dose to the embryo/fetus and assessing the dose delivered.
(22) The present publication covers the application of digital radiology to medical diagnostic
and interventional applications. The content will replace material in Publication 93 on technicalissues in digital radiology, and Publications 87 and 102 on CT, and will supplement material
in Publications 85, 117 and 120 linked to specific applications of fluoroscopy andinterventional procedures, Publication 121 on paediatric imaging, and Publication 135 on
DRLs. The document does not include mammography for which detailed specialist texts areavailable, the application of imaging in radiotherapy treatment, which will be covered in a
future publication (ICRP TG116), or dental radiology.
(23) The dosimetric quantities used with the various modalities are listed in Annex A. The
tools that accompany digital imaging from Radiology Information Systems (RIS), to Picture
Archiving and Communication Systems (PACS), and Dose Management tools facilitate
workflow, allowing easier storage and transfer of image data, image manipulation and merging,
and recording of exposure details, are described in Annex B.

12

DRAFT REPORT FOR CONSULTATION: DO NOT REFERENCE

2. DIGITAL RADIOGRAPHY

427
428

(24) Key messages in this section:

429
430
431
432
433

•

Digital radiography facilitates the storage and transfer of image data and recordingof exposure details, as well as offering more flexibility in exposure. Digitalradiography (DR) has a wider dynamic range than film, allowing for adjustment ofimages after exposure. As a result, it is the noise level and image contrast that set thelimits on image quality.

434
435
436
437

•

Selection of tube potential is a compromise between competing requirements, suchas contrast and penetration, and appropriate combinations of tube potential andmAs should be established for different anatomical regions and patientcharacteristics, and linked to the clinical question to be answered.

438
439
440

•

Grids are used for most adult radiography examinations, but may be dispensed withfor examinations of small children. “Virtual grid” software can be useful where there
are practical difficulties in mobile radiography, but will not replace the physical grid.

441
442
443

•

Additional copper filters (0.1–0.3 mm) can give reductions of 20–50% in effective
dose with tube potentials of 70–80 kV by removing low energy photons and arerecommended routinely for paediatric examinations.

444
445
446
447

•

AEC devices should be calibrated to suit the characteristics of the detector and canbe set up to maintain a constant Exposure Index. The initial setting is crucial indetermining exposure levels and all chamber combinations should be tested
regularly with phantoms representing a range of patient thicknesses.

448
449
450

•

The target exposure index (EIT) represents the optimal exposure for a particularbody part being imaged, patient characteristics, and imaging task. EIT values should
be determined by the optimisation team and will depend on the noise level required.

451
452
453
454

•

The central importance of collimation on patient dose and image quality should beemphasised throughout radiographer training. Suboptimal practice should be
identified through regular audit of kerma-area product (KAP) against expected goodpractice values.

455
456

•

The use of patient gonadal shielding during x-ray based diagnostic imaging should
be discontinued as routine practice.

457
458
459
460

•

Data on rejected images should be collected and analysed regularly. Reject rates
should be calculated and quality improvement actions taken when they rise above apredetermined threshold. Reasons for rejects should be used to steer improvements
in working methods.

461
462
463
464
465

•

Acceptance testing and commissioning are crucial to ensure new equipment isperforming optimally. After commissioning, medical physicists and radiographers
should work together to establish a local QC/QA programme. Radiographers,
radiologists, and medical physicists should collaborate to identify the mostappropriate processing algorithms for reporting radiographs.

466

2.1. The digital radiography system

467(25) Radiography is the fundamental radiological imaging process and is in widespread use
13

DRAFT REPORT FOR CONSULTATION: DO NOT REFERENCE

468
469
470
471
472
473
474
475
476
477
478
479
480
481
482

throughout the world in different types of facility. The move from film to digital imaging has
simplified the sharing of images, and reduced running costs and material consumption. Digitalradiography facilitates the storage and transfer of image data and recording of exposure details,
as well as offering more flexibility in exposure, enabling levels to be adapted to the diagnostic
requirements of particular examinations.
(26) There are typically multiple radiography rooms in larger hospitals, and smaller
hospitals and clinics that have their own radiographic room or mobile unit. Thus, there arebroad ranges in facilities using radiography, with different radiographic equipment, and varying
levels of experience of personnel who carry out the procedures. The setting up of a new
installation requires careful planning by a team of radiological professionals, and arrangements
for this are described in Section 2 of Publication 15x (ICRP, 2022).
(27) Digital radiography systems have significantly broader dynamic ranges than film andthe grey levels in the displayed image can be adjusted for optimal viewing through postprocessing independent of exposure (Fig. 2.1). As a result, it is the noise level and image
contrast that set the limit on image quality.

483
484
485
486

Fig. 2.1. Presentations of the same chest image using different post processing look up tablesusing an underexposed appearance at left, overexposed in middle, and optimised image at right(Dean Pekarovic, University Medical Centre Ljubljana, Slovenia).

487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509

(28) The digital radiography systems available are described briefly in Box 2.1. In many
hospitals the first stage in the introduction of digital radiography is the installation of computed
radiography (CR), as this can be used with existing x-ray equipment, the film/screen cassette
simply being exchanged for a CR one. However, the x-ray unit automatic exposure control(AEC) system should be recalibrated to suit the characteristics of the CR or direct digitalradiography (DR) detector – a point that is often overlooked (ICRP, 2004; Doyle and Martin,
2006; IAEA, 2015). Full DR systems offer more detailed preinstalled protocols including not
only tube kV and mAs selection, but source image-receptor distance (SID), additional filtration,
field of view (FOV), position of image receptor, use of radiographic grid, and post processing
tools.
(29) Digital systems allow for digital archiving, and in many hospitals digital images areheld centrally on PACS systems and images viewed on workstations. As a result, radiologists
and radiographers find themselves in separate rooms. This can be detrimental to regularcommunication, education, and QA, and this should be borne in mind when new facilities arebeing set up. Regular exchange of information between radiographers and radiologists, enables
complaints about poor image quality and comments on what can be improved in radiographic
technique to be fed back and changes implemented. This link is crucial, especially in relation
to specific clinical indication examination protocols (Image Wisely, 2022a, case 4).
(30) CR and DR images are reviewed by radiologists on diagnostic quality displays(DICOM calibrated), but the display on the radiographers’ console may not be of a similar
quality and illumination conditions in the acquisition room may not be ideal. Images on
diagnostic displays may be larger in size with a higher pixel count, more greyscale levels, andbetter image reproduction. If images viewed by radiographers are of a poorer quality, it will
14

DRAFT REPORT FOR CONSULTATION: DO NOT REFERENCE

510
511
512
513

be more difficult for them to appreciate subtle effects or even artefacts that might be corrected.
For effective control of digital radiography systems, radiographers should have access toreview diagnostic quality displays, on which all exposure parameters are visible, and adaptableroom illumination conditions with the capability for dimming.
Box 2.1. Digital radiography technology
Computed radiography (CR): The image is stored on a photo-stimulable phosphor (barium
fluorohalide) plate and converted to digital form later using an image plate reader.
Digital radiography (DR): The image recorded is stored directly in a diode array within theimaging detector. The image receptors contain phosphors or photodiodes that convert x-ray
energy into light or an electrical signal that can be recorded (ICRP, 2004; EC, 2004; IPEM,
2010). The types of system can be subdivided into:o Indirect X-ray capture digital radiography (IDR): IDR systems contain a phosphor platebacked by a diode array. Caesium iodide (CsI) imaging plates used in many DR systems
have thicker phosphor layers with needle shaped crystals and are substantially moresensitive than systems using gadolinium oxysulphide (Gd2O2S) or other phosphors(ACR-AAPM-SIIM-SPR, 2017).
o Direct x-ray capture digital radiography (DDR): DDR systems comprise a conductive
layer of a semi-conductor, such as selenium or cadmium telluride, backed by an array ofelectrodes. X-ray photons are converted into electron-hole pairs in the semi-conductor(Queiroz et al., 2020).

514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533

(31) The measurable quantities used to monitor patient dose in radiography are incident air
kerma at patient entrance surface (IAK, Ki), the entrance surface air kerma (ESAK, Ka,e), which
may be calculated from exposure factors or measured with dosemeters, and the kerma-area
product (KAP, PKA) measured by a meter attached to the output port of the x-ray unit. These
are listed in Annex A and more information on their use is given in ICRP (2017, 2022).
(32) Since the greyscale level is optimised in digital radiography, the primary feedback on
exposure, unless a KAP meter is fitted, will be through the exposure index (EI) (Section 2.2.3;
IEC, 2008; AAPM, 2009; Dave et al., 2018,). The EI is a measure of radiation incident on theimage receptor (see Section 2.2.3) and so reflects the noise levels present in the image.
Although the EI will be related to the KAP values, it should not be considered as a surrogate
for dose (Annex A). Monitoring of EI, together with periodic auditing of KAP or ESAK is
essential to keep track of any changes in exposure conditions and dose level (Cohen et al, 2011;
ICRP, 2017; AAPM, 2018). EI values will vary with the type of examination (Jamil et al. 2018),
but will vary less with patient size than measured dose quantities, and deterioration in theperformance of CR cassettes with time will be apparent through change in the EI.
(33) The change from film to digital technology offered an opportunity to optimise patient
dose. However, there was often a tendency for the dose to rise or remain the same, rather thanfall. The transition requires a critical examination of procedures, technical issues, andestimation of doses, together with comprehensive training in radiographic techniques, followedby regular QC tests, to ensure effective use is made of the system (ICRP, 2004; IAEA, 2015).

534

2.2. Optimisation of exposure factors and radiation quality535

2.2.1. Tube potential and mAs

536(34) X-ray beams used for medical imaging contain photons with a wide range of energies
15

DRAFT REPORT FOR CONSULTATION: DO NOT REFERENCE

537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557

determined by the x-ray tube potential and filtration. Lower energy x-ray photons provide good
contrast between tissues of differing compositions, but are more heavily absorbed. Higher
energy photons do not interact as strongly in tissue, and tend to give more scattered radiationand poorer contrast, but they will penetrate more deeply through tissue. The maximum energy
is determined by the tube potential. The product of the tube current and exposure time, usuallyreferred to as mAs, controls the number of photons emitted from the x-ray tube. For a given
tube potential, the mAs will determine the number of photons reaching the image receptor andso the level of quantum noise in the image. If a higher tube potential is used for a particular
projection, the mAs can be reduced to give a similar exposure at the image plate with a lower
patient entrance dose. The contrast will decrease and the amount of background scatteredradiation will increase, so the choice of tube potential is a compromise between the competing
requirements (Martin, 2007; ICRP, 2022). Appropriate combinations of kV and mAs should beestablished for different anatomical regions and patient characteristics, and linked to theclinical question to be answered.
(35) The choice of tube potential is a crucial component of optimisation in radiology. Tubepotentials of 70 kV to 90 kV will generally be used for exposures of the trunk, with values
being increased for larger patients; 50 kV or 60 kV will be used for extremities; and 55 kV to
70 kV for premature infant, neonatal, and infant chest/abdomen radiography. However, the tube
potential values are higher (kV 120–140) when a grid is used for chest images on fixedradiographic units (anti-scatter grid of at least 10:1, preferably 12:1) (ACR-SPR-SIIM-STR,2017) (Box 2.2).
Box 2.2. Choice of the correct grid
A grid consists of a plate containing thin strips or lamella of lead lying perpendicular to thesurface, sandwiched between layers of a low attenuation inter-space material such as fibreor paper. X-rays scattered at angles are attenuated by the lead strips.

Grids are categorised by the strip density in lines per cm and the grid ratio. Strip densities
less than 45–60 lines per cm require mechanical movement to prevent the appearance of lines
on the image due to aliasing. A typical value used for general radiography would be 40 lines
per cm and the grid would be mounted within a Bucky that would provide the movement.
The grid ratio determines the effectiveness of the grid in removing scattered radiation, butalso affects the transmission of the primary beam. Grid ratio depends on the modality andthe source to imaging distance (SID). When there is less scatter, a lower grid ratio (8:1) witha lower tube potential will give the desired contrast level. Ratios of 10:1 or 12:1 are usedcommonly for table or wall mounted Buckies, and 6:1 or 8:1 for imaging with mobile units.
Grids can often be removed for paediatric patients or extremities, where there is less scatter.
The strips may be parallel or angled so that the grid is focussed towards the focal spot of the
x-ray tube to improve transmission. The correct source to image receptor distance must be
used to avoid cut-off of transmission at certain angles.
558
559
560
561

(36) The highest tube potential within the optimal range for the position should be used,
coupled with the lowest mAs needed to provide an adequate exposure to the image receptor(Herrmann et al., 2012). Examples of ranges of tube potential recommended for imaging
different parts of the body, together with other information about the exposures, are given in
16

DRAFT REPORT FOR CONSULTATION: DO NOT REFERENCE

562
563
564
565
566
567
568
569
570
571
572
573
574
575
576

Table 2.1. The values in the table are approximate and included to provide guidance on levels
that might be expected, rather than target values. They are based on a variety of sources
including EC (1995, 2004) and Herrmann et al (2012). The exposure parameters set should beappropriate for the type of detector in the image receptor (Box 2.1). Combinations of tube
potential and mAs should be established for different anatomical regions and possible patientcharacteristics and exposure charts prepared for a full range of examinations for each x-ray
unit. The level of image quality in terms of contrast and noise level required will depend on theclinical question to be answered. For example, the initial evaluation of a fracture without any
displacement will require a high level of image quality, and perhaps additional image exposures,
whereas for other orthopaedic applications where the contrast is high a lower level of image
quality will be adequate. The level of image quality can be defined as high, medium or low
according to clinical task being undertaken and the mAs chosen accordingly (EC, 2004; Buschand Faulkner, 2005; Uffmanna and Schaefer-Prokop, 2009). Exposures for some routine
follow-up studies where the image quality required can be judged from previous images (e.g.,
for pneumonia or tube positioning) can be reduced substantially.

577

Table 2.1. Exposure factors and expected dose levels for a range of imaging tasks.
ESAK*
(mGy)

KAP*
(Gy cm2)

Yes

0.05–0.2

0.06–0.1

75–85

No

0.3–0.5

0.06–0.1

AP

75–90

Yes

2–6

0.7–1.5

Lumbar spine

lateral

80–95

Yes

5–10

1.4–2.5

Abdomen

AP

75–90

Yes

2.5–5

1.4–2.5

Pelvis

AP

75–90

Yes

2–4

1.3–2.2

New-born <5 kg

AP/PA

56–65

No

0.1–0.2

0.03–0.07

0.003–0.015

Infant 5-15 kg chest(4 m–3 y)

AP/PA

60–80

No

0.1–0.2

0.04–0.08

0.005–0.022

AP

60–80

No

0.1–0.2

0.3–0.6

0.05–0.15

AP/PA

70–85

No

0.1–0.2

0.06–0.12

0.008–0.05

AP

70–80

Yes

0.1–0.2

0.5–1.5

0.15–0.25

AnatomyProjection

kV

Grid

Chest

PA

120–140

Chest

PA

Lumbar spine

Infant 5–15 kg abdomen
pelvis (4 m–3 y)Child 15-30 kg chest(4 y–10 y)Child 15–30 kg abdomen
pelvis (4 y–10 y)
578
579
580
581

Additional
filtration(mm Cu)*Dose quantities represent a range of average values (1st and 3rd quartile values in a dose survey) andthe adult ones are for a 70 kg patient. If an indirect DR system with CsI is used, then values should be
towards the lower end of the range or lower. PA – postero-anterior, AP - antero-posterior. Doses from
improved modern systems may go below the values listed.

17

DRAFT REPORT FOR CONSULTATION: DO NOT REFERENCE

582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622

(37) Scattered radiation reduces contrast in radiography, limiting the dynamic range of x-ray
intensities that is available. Grids are employed to absorb the scattered radiation to improve
contrast (Box 2.2) and are used for the majority of adult radiography examinations of the trunkor head, but are not required when imaging thicknesses of soft tissue less than about 12 cm or
low attenuation exams with low tube potentials (Table 2.1). Thus, grids are used for most adultradiography examinations, but may be dispensed with for examinations of small children.
Modern DR systems may also incorporate virtual grid algorithms where the effect of scatter iscorrected computationally in the acquired images (see Section 2.3.3).
(38) Grid cassettes are used with mobile units in which the grids are lighter and easier tohandle. Since grids attenuate the transmitted x-ray beam and the specifications vary, exposure
factors need to be adjusted upward to suit the arrangement. The regular lines in a grid can
combine with the array of detector elements in the image receptor to produce an artefact withregular lines known as "aliasing" caused by insufficient sampling.
(39) If a mixture of grid and non-grid exposures are carried out on the same unit, there should
be a safety check before an image is taken to ensure that the unit is set up correctly. An agreed
system, such as replacement of the grid after all non-grid exposures, can minimise the risk.
Some equipment displays an icon to show whether the grid is in place.
(40) In order to achieve a consistent exposure level, an automatic exposure control (AEC)
device is usually employed in fixed radiographic imaging facilities that terminate exposures atpredetermined levels (Section 2.2.2). AEC devices have settings that allow the exposure level
to be decreased or increased, and these can be used to select lower or higher exposures forparticular types of examination.
(41) Different values of tube potential may be selected depending on the imaging task, forexample a slightly lower tube potential may be used to visualise a rib fracture than that required
for soft tissue imaging. Tube potential and mAs values need to be adjusted together and finetuned when establishing exposure factors for use in a facility. Increasing tube potential without
decreasing mAs will result in a higher dose to the patient, as output increases roughly as kV2.
If significant changes are to be made, assessments should be carried out on clinical image
quality. Anthropomorphic phantoms, if available, can be useful for this and criteria have been
established for such assessments (EC 1995, 2004)(42) Metal filters are placed in x-ray beams to attenuate lower energy photons few of whichreach the image receptor (Box 2.3). These are incorporated as standard in medical x-ray tubes
and a minimum total filtration, which includes that inherent in the x-ray tube itself, is usuallyspecified in regional/country regulations. For example, 2.9 mm of aluminium equivalent halfvalue layer (HVL) at 80 kV is required for x-ray tubes in the USA, whereas 2.5 mm aluminium
equivalent total filtration is the minimum requirement in the UK.
(43) Additional copper filters (0.1–0.3 mm) can give reductions of 20–50% in effective dosewith tube potentials of 70–80 kV by removing more low energy photons and are recommended
routinely for paediatric examinations and for adults with CsI DR systems. However, adding
excessive copper filtration can result in reduction of image contrast with less differential
between grey tones.

623

2.2.2. Automatic exposure control (AEC)

624
625
626
627
628

(44) AEC devices are employed to control exposures and improve the consistency of image
acquisition. An AEC usually comprises a set of three x-ray sensors behind the patient thatmeasure the radiation incident on the image receptor (behind any grid). The sensors are thin
ionisation chambers, two to the upper right and left (over the lungs in chest radiography) and
one usually lower down in the centre (over the spine). The number and position of the x-ray
18

DRAFT REPORT FOR CONSULTATION: DO NOT REFERENCE

629
630
631
632

sensors may vary among x-ray units. Exposures are terminated when a pre-determined doselevel is reached, in order to ensure that consistent exposures are given to the image receptor forpatients of different sizes. Use of AECs is recommended whenever possible although smallchildren may require manual techniques.
Box 2.3. Additional metal filters
Copper absorbs more lower energy photons in the 20–50 keV range than aluminium andinclusion of a 0.2 mm thick copper filter in radiographic units can reduce entrance surface
air kerma (ESAK) and KAP by 50%. The reduction in effective dose for examinations of thetrunk will be 40% with tube potentials of 70–80 kV, and 25% at 120–130 kV (Samei et al,2005). The images below depict radiographs taken with and without copper filtration andshow minimal change in image quality, but substantial reductions in KAP. Use of additional
copper filtration has the advantage of lowering dose if the DR unit is properly optimised
and it is recommended for units used for paediatric examinations (Section 5.2). It will also
reduce ESAK and KAP for adult examinations, but copper filtration has the disadvantagethat the mAs must be increased in order to maintain the same level of quantum noise.
This may only be appropriate for higher sensitivity CsI DR systems (Box 2.1). The tube
output at 80 kV would need to be increased by 15%–20% for 0.1 mm of copper or 20%–
30% for 0.2 mm of copper and this may have an impact on the x-ray tube lifetime andpossibly lengthen exposure times.
If any additional filtration is incorporated into a system, the image quality and AEC settings
should be evaluated thoroughly before the system is introduced into clinical practice toensure that the diagnostic quality of the images is not compromised (EC, 2004).
Additional copper filters for clinical use are mounted in the tube housing before the KAP
chamber. If a filter is placed after the KAP meter during initial trials to investigate the effecton images of a phantom, the KAP value will not record the dose reduction.

Fig. Pelvic radiographs taken at 81 kV with a Siemens Axiom Aristos FX showing the effectof additional copper filters. Exposures from left to right were taken with the following
thicknesses of copper 0 mm, 0.1 mm, 0.2 mm, and 0.3 mm, and KAP values are 34 cGy cm2,
22 cGy cm2, 14 cGy cm2, and 11 cGy cm2, respectively (cadaver study- Dean Pekarovic,
University Medical Centre Ljubljana, Slovenia).
633
634
635
636
637
638
639
640

(45) AEC devices should be calibrated to suit the characteristics of the detector and can be
set up to maintain a constant Exposure Index (see Section 2.2.3, Fig. 2.2). The initial setting is
crucial in determining exposure levels and all chamber combinations should be tested regularly
with phantoms representing a range of patient thicknesses to ensure consistency.
(46) The variation in sensitivity of a digital detector with photon energy and so tube potential
depends on the phosphor material. While the sensitivity of CsI DR systems increase with tube
potential, that for CR systems decline, so the relative exposure needs to be increased slightly
at higher tube potentials (Doyle and Martin, 2006). The exposure index (EI) for digital imaging
19

DRAFT REPORT FOR CONSULTATION: DO NOT REFERENCE

641
642
643
644
645
646
647
648
649
650
651
652
653
654
655
656
657
658
659
660
661
662
663
664
665
666
667
668
669
670
671
672
673

systems relates to the level of image quality and the relative response at different tube potentials
follows a similar pattern to the signal-to-noise ratio (SNR) (Section 2.2.3). Therefore,
maintaining a constant EI is recommended as the method of choice for setting up AECs for
digital radiography.
(47) The noise level in the image and the SNR are determined by the image receptor
sensitivity and the exposure level and the AEC should be used to achieve the desired level ofimage quality. AEC calibration curves are stored in the memories of x-ray generators to suitthe energy dependence of different digital radiography systems and the AEC should be set up
at installation of a new type of image receptor. AEC devices are usually set up relative to apredetermined air kerma incident on the detector at 80 kV, and use different kV compensation
curves, so that the AEC can be calibrated according to variations in detector sensitivity withtube potential. The initial setting of image receptor dose levels at 80 kV is crucial indetermining the overall exposure level for radiographic imaging in a department. The images
need to achieve the correct balance between image quality and dose, so involvement of all
members of the core imaging team (radiographers, radiologists and physicists) is crucial.
(48) Considering quality levels required for different imaging tasks, high might correspondto an air kerma incident on the image receptor of 0.2–0.5 mGy, medium to 0.1–0.25 mGy, andlow to 0.05 to 0.12 mGy. The lower end of each air kerma range might correspond to that
required for a DR system and the upper end for a CR system. The majority of AEC systems
allow the exposure level to be decreased or increased in steps of 20%–30%. These canpotentially be used to adjust the exposures to give lower or higher levels for imaging tasks
requiring different image quality levels.
(49) The AEC chambers selected will depend on the examination and the exposure level
required in the region of interest. In modern units the chambers used, together with exposure
factors will be preselected for different examinations. All combinations must be calibrated andthereafter tested regularly to ensure consistency between different chambers, using a variety oftube potentials, and with phantoms representing a range of patients’ thicknesses (IPEM, 2010).
(50) A common mistake in use of an AEC is not centring the anatomical area of interest on
the relevant chamber. There may be greater risks for certain examinations, for example inlateral spine projections, when patients are lying on a table or trolley. A special group are
paediatric patients, in whom there is a possibility that the AEC chamber and the anatomy may
not overlap (Section 5.2). In cases when there is a significant risk of misaligning the anatomy
and AEC chamber, use of the manual technique is recommended.

674

2.2.3. Exposure Indicator

675
676
677
678
679
680
681
682
683
684
685
686
687

(51) Digital radiographic imaging systems can produce adequate image quality over a broad
range of exposure levels, the only difference being in the noise levels. Images having higher
or lower noise levels than is required are not readily recognizable at the time images are taken,
so there a risk of dose creep and increases of 40% in dose have been reported (Gibson andDavidson, 2012). Exposure indicators have been developed by manufacturers of digital image
detectors and later standardised following the recommendation of AAPM Task Group 116(AAPM, 2009) and more recently AAPM Task Group 232 (Dave et al., 2018).
(52) The detector exposure indicator is intended to reflect the exposure level at the image
receptor within the relevant image area to facilitate the production of consistent, high quality
digital radiographic images. More specifically, the exposure index (EI) is related to the air
kerma in µGy at the image receptor in the anatomical region of interest within the image andso is a linear function of tube current. It should be noted that the EI depends on the body partselected, the body part thickness, the tube potential, the added filtration in the x-ray beam, and20

DRAFT REPORT FOR CONSULTATION: DO NOT REFERENCE

688
689
690
691
692
693
694

the type of detector, among other factors. Since it is related to the air kerma incident on theimage receptor, it provides a measure of signal acquisition and thus, it is suitable for monitoringchange in imaging performance. The relevant region of the image for calculation of the EI is
identified through segmentation of the relevant anatomical image area and the EI equated tothe dose corresponding to the median of the distribution of pixel values within this area ofinterest (IEC, 2008; Dave et al, 2018). Comparisons can be made with an intended target value(EIT) and a deviation index (DI) derived as:
𝐷𝐼 = 𝑙𝑜𝑔10 (

695

𝐸𝐼
)
𝐸𝐼𝑇

696
697
698
699
700
701
702
703
704
705

(53) The target exposure index (EIT) represents the optimal exposure for a particular bodypart being imaged, patient characteristics, and imaging task. EIT values should be determinedby the optimisation team and will vary to some extent for different x-ray procedures performed,
as it depends on the noise level required for the task. Default values of EIT are set by the vendor,
and these should be tested and adjusted for optimisation by the user for each anatomical region
during the commission of a new x-ray equipment. During clinical use, the deviation index (DI)should be used by radiographers to identify images that are under or over exposed so thatappropriate action can be taken (Table 2.2). A DI of 0 indicates the proper exposure, a DI above+1 a higher exposure than expected and a DI less than −1 is lower. Actions relating to different
DI values are listed in Table 2.2 (AAPM, 2009).

706
707

Table 2.2. Recommended values of Deviation Index (DI) for determining acceptable
imaging settings and required actions (AAPM, 2009)
DI

Action required> +3

Excessive patient radiation exposure. Repeat only if relevant anatomy is clipped or“burned out”. Require immediate quality assurance (QA) management follow-up+1 – +3

Overexposure. Repeat only if relevant anatomy is clipped or “burned out”.

−0.5 – +0.5

708
709
710
711
712
713
714
715
716
717
718
719
720
721
722

Target range<−1

Underexposure. Consult Radiologist for possible repeat<−3

Repeat (consider QA programme)(54) It is important for radiographers and radiologists to understand the usefulness of
exposure indicators, how they can be used, and their limitations. The EI is not a single measureof image quality as it is affected by many parameters, nor is it a patient dose indicator. There
have also been vendor specific definitions for EI, so users of older equipment should be awarethat factors may be different.
(55) EI is a tool for quick assessment of the appropriateness of an exposure and monitoring
exposure levels. The EI is included in the DICOM header of radiographic images and, together
with dose (KAP), is useful for optimisation purposes (Fig. 2.2). The DI can be calculated anddisplayed on the interpreting workstation/PACS. By recording and monitoring exposure
indicators and values of DI, facilities can control dose creep. Analysing the percentage ofimages that fall outside an acceptable range can be used to educate technologists and decrease
the variation while improving image quality goals of the department.
(56) It should be noted that the value of EI can be quite dependent on the manufacturer. In
addition, the definition has evolved with time and older CR systems from different
manufacturers used completely different definitions. The user needs to know how their system
21

DRAFT REPORT FOR CONSULTATION: DO NOT REFERENCE

723
724

performs and obtain calibration tables for EI versus dose to detector or noise in a simple
phantom, if there are uncertainties, or if different manufacturers cohabit in the same facility.
Procedure
T084 Pelvis AP
T084 Pelvis AP
T026a Lumbar-spine AP
W019a Cervical-spine AP
T090a Hip AP
W019b Cervical-spine Lat
W050 Shoulder joint AP
L026b Lumbar-spine Lat
L026b Lumbar-spine Lat
T026a Lumbar-spine AP

Number
238
188
171
147
137
131
131
130
124
106

KAP_average2(µGy.m )
44.7
48.1
43.6
7.04
25.5
6.25
8.7
187
163
56.1

KAP_medianDRL
22(µGy.m ) (µGy.m )
39.4
200
42.6
200
35.4
130
6.0
30
24.0
95
5.7
35
7.6
30
155
230
150
230
47.7
130

KAP_med/DRL
0.20
0.21
0.27
0.20
0.25
0.16
0.25
0.68
0.65
0.37

EI_average
340
322
327
269
312
326
387
360
395
321

725
726
727
728
729

Fig. 2.2. A spreadsheet chart used for monitoring KAP and EI values for selected radiographic
examinations. The exposure index target value (EIT) was set at 250, but could be modified by
the user for each projection. (Urban Zdešar, University Medical Centre Ljubljana, Slovenia,
reproduced with permission).

730

2.3. Other aspects of optimisation731

2.3.1. Source to image receptor distance (SID) and focal spot size

732
733
734
735
736
737
738
739
740
741
742
743
744
745
746
747
748
749
750
751
752
753

(57) The intensity of the x-ray beam is related to the SID by an inverse square law. In
modern radiographic rooms a fixed SID is normally used, with 100 cm being in widespreaduse, although some manufacturers recommend 110–115 cm, which will reduce the ESAK anddetector dose by about 20% (Carroll, 2018), but this must be in concordance with the grid focus.
Changing the beam geometry by extending the SID from 100 cm to 115 cm will improve spatial
resolution (less blurring) and decrease magnification. For mobile radiography, the radiographer
should adjust the mAs according to the inverse square law formula. As a rule of thumb thisinvolves increasing the exposure by 20% if the SID is lengthened by 10 cm and reducing it by
20% if the SID is shortened.
(58) Increasing the SID can be used to reduce image magnification in order to include thecomplete anatomy within the image for large patients. The inverse square law should be used
to achieve the same dose at the image receptor, although if the patient is large then it may beappropriate to increase the tube potential as well. However, the grid focal distance should betaken into account in determining the correct SID.
(59) X-ray tubes are typically provided with two focal spot sizes linked to the apparent sizeof the imaging source that is related to the tube filament size. The small focal spot should be
used for clinical indications where visualisation of subtle anatomical detail is required, when
the tube loading allows –such as with small body parts in musculoskeletal DR, and if the
prolonged exposure time is acceptable regarding patient motion. Some reports suggest thatdifferences between small and large focus are not visible in DR, but experienced radiologists
observe more blurred details when a large focus is used and the image is viewed on a diagnostic
display.

754

2.3.2. Field of View (FOV) and Collimation

755(60) Essential to every radiographer’s training is the importance of collimating the x-ray
22

DRAFT REPORT FOR CONSULTATION: DO NOT REFERENCE

756
757
758
759
760
761
762
763
764
765
766

beam to the anatomy to be imaged. This is facilitated for CR by the wide range of cassettes
available, which encourages radiographers to consider image size, but DR image receptors areusually only available in two plate sizes 43 cm × 35 (or 43) cm and 24 cm × 30 cm and thiscan encourage poor practice. Recently, more DR receptor options such as neonatal chest
receptors are being offered but they are expensive. Radiographers have a simple tool available
to crop DR images, and it is easier in practice to use a larger FOV and crop the images. Usinga larger FOV than necessary will not only result in unnecessary exposure of more tissues
surrounding the area being imaged (and give a higher KAP), but it will also produce more
scatter from the surrounding tissues and so degrade the image quality (Shields and Bushong,2012). Poor collimation in images of neonates is prevalent in some centres and can lead to
unnecessary exposure of adjacent tissues, as shown in the example in Fig. 2.3a and b.

767
768
769
770
771
772
773
774
775
776

a
b
c
d
Fig. 2.3. Issues in image collimation. 2.3a and b show a portable babygram in a neo-natal
intensive care unit to determine umbilical vein catheter placement position; a) The original
image which is poorly collimated, and b) image with the appropriate collimation (KimberlyApplegate, USA). 2.3c and d exemplify very poor practice. They show an ostensibly collimatedimage which is in fact cropped. C shows the image with a normal window width and level,whilst d shows the image with an adjusted window width and level, demonstrating the actual
radiograph as exposed. Images of this type can be used for auditing poor collimation practicewhere this is an issue (Dean Pekarovic, University Medical Centre Ljubljana, Slovenia).

777
778
779
780
781
782
783
784

(61) The central importance of collimation for patient dose (and KAP values) and image
quality cannot be overemphasised throughout radiographer training. Suboptimal practice
should be identified through regular audit of KAPs against expected values. In departments
where collimation practice is suboptimal, examples of good versus poor collimation DR and atable showing how larger FOVs affect KAP could be displayed. Radiographers should be awarethat through differences in KAP values and adjustments of windowing in CR to show theoriginal FOV for non-collimated images, poor practice can be identified during audits (Fig 2.3c
and d).

785

2.3.3. Virtual Grids

786
787
788
789
790
791
792
793

(62) Some vendors offer “virtual grid” software, sometimes called “grid less” or “scattercorrection” software, which incorporate algorithms to reduce scatter in the acquired images(Mentrup et al., 2014). Some algorithms are based on Monte Carlo simulations of the passageof x-rays through water and a calibrated correction step that is tailored to mimic the propertiesof an anti-scatter grid. A grid-adapted scatter image is then subtracted from the original detector
image to reduce scatter content. However, virtual grid algorithms vary significantly between
vendors and some are only simple post-processing operations. Therefore, the application ofvirtual grids should be considered separately for each examination type and equipment model.
23

DRAFT REPORT FOR CONSULTATION: DO NOT REFERENCE

794
795
796
797
798
799
800
801
802
803
804
805

Virtual grids may enable more extensive radiographic imaging without grids and help tomaintain sufficient image quality as regards to scatter, e.g. in mobile chest x-ray imaging.
Examples of chest images before and after application of a virtual grid are shown in Fig. 2.4
and images obtained with a standard and a virtual grid are compared in Fig. 2.5.
(63) Virtual grid software can be useful in situations where there are practical difficulties intaking a radiograph and the lower quality of the image obtained is still acceptable. This may bewhen the patient cannot cooperate for positioning, is on a trolley or bed, or in the case of trauma,
either in the radiology department or with mobile units. Virtual grid software will allow lower
exposure factors to be used, although this should not be a reason for not using a physical gridwhere one is required. If a grid is removed from a bucky for any reason, then a check must be
carried out afterwards to ensure that it is replaced and in the correct orientation before a newpatient is imaged.

806
807
808
809
810

811
812

a

b

Fig. 2.4. Chest images a) before and b) after application of virtual grid software demonstrating
improved image quality in figure b (Philips –Skyflow) (reproduced with permission from
Koninklijke Philips N.V.).

a

b

813
814
815

Fig. 2.5. Comparison of images of two patient knees obtained a) with an actual grid and b) with
virtual grid software (Philips –Skyflow). Both radiographs show high image quality (Dean
Pekarovic, University Medical Centre Ljubljana, Slovenia).

816

2.3.4. Patient protective equipment (shielding devices)

817
818

(64) The use of patient gonadal shielding during x-ray based diagnostic imaging should be
discontinued as routine practice. The reason for this is that it provides little benefit to patients’24

DRAFT REPORT FOR CONSULTATION: DO NOT REFERENCE

819
820
821
822
823
824
825
826
827
828
829
830
831
832

health, exposures per DR examination have declined, and shielding can negatively affect theefficacy of the examination (AAPM, 2019c). Moreover, there is no evidence of human heritableeffects resulting from exposure of the gonads (ICRP, 2007b). However, ICRP task group 121
will review the recent literature on radiation risk to the offspring and future generations. Patientshielding is ineffective in reducing internal scatter which is the main source of radiation doseto internal organs that are outside the imaging FOV (Marsh and Silosky, 2019; Hiles et al, 2020,
2021; NCRP, 2021). The shielding may obscure pathology, introduce artefacts that will degrade
image quality and image processing in digital radiography, or interfere with the exposure of an
AEC chamber, thereby increasing the dose. Contact shielding is not generally recommended,and the effectiveness of shielding outside the FOV is minimal. However, consideration should
be given to protection of the breast, gonads and thyroid where these organs lie within 5 cm of
the primary beam (ICRP, 1982, 2013b) (Table 2.3). More efficient optimisation methods on
modern digital imaging equipment with specific dose reduction options and conventional dosemanagement features can be implemented including attention to close collimation.

833
834

Table 2.3. Recommendations for patient shielding in diagnostic radiology (Hiles et al, 2020,
2021)
Scenario

835
836
837
838
839
840
841
842
843
844
845

Recommendation

Comments

Patient contact
shielding forprotection of breast

Not recommended Use PA positioning rather than shielding for spinal andchest examinations where possible. If using AP
projection then a Scoliosis shawl may be considered.

Patient contact
shielding forprotection of thyroid

Not generally
recommended

Patient contact
shielding forprotection of gonads

Not recommended Male adult and paediatric patients: May be considered
where gonads are less than 5 cm from the primarybeam. Female adult and paediatric patients: Not
recommended for imaging in the pelvic region.

Patient contact
shielding forprotection of eye lensNot recommended Use PA skull positioning, no recommendations forshielding.

Pregnant patients

Not recommended For examinations within pelvic region (from diaphragm
to knee), consider non-ionising imaging alternatives. If
ionising radiation must be used carry out a thoroughjustification and risk assessment process.

May be used for paediatric patients in cephalometricradiography if evaluation of the cervical spine is notneeded or obscured. The effectiveness of shielding
outside the FOV is minimal and potential interferenceof the shield with the AEC must be avoided.

(65) Patients or carers may be more comfortable if gonadal shielding is used, as it has beena rule of good practice for many decades, but this is not a reason for resisting the change inpractice. Changing the practice will take time, requiring stakeholder education and raisingawareness of professionals such as clinicians and radiographers, as well as of carers, patientsand families.
(66) During training, radiographers must be aware that not only gonadal shielding but
anything which is not part of the requested anatomy must be removed when possible or at least
moved out of the FOV, especially when there is a risk of it lying over an AEC chamber. This
includes limbs, which if incorrectly positioned may overlie important anatomy (Image Wisely,2022). For chest x-rays with lateral projections and elderly patients requiring to use the support
bar when standing, the position of the arms should be checked. If arms are flexed too much at
25

DRAFT REPORT FOR CONSULTATION: DO NOT REFERENCE

846
847

the elbows, they can affect image quality and AEC chamber performance.

848

2.3.5. Reject analysis

849
850
851
852
853
854
855
856
857
858
859
860
861
862
863
864

(67) A reject and retake analysis programme should be in place to allow radiographers tolearn when images are suboptimal or non-diagnostic. The move to digital radiography shouldhave decreased the number of repeat radiographs in theory, because of the wide exposure
latitude. However, this has not been the case as image acquisition is easier and facilitates theease of taking repeats. The analysis of rejected images in digital radiography is complex andtime consuming (Jones et al., 2015; AAPM, 2015). There may no longer be physical evidenceof rejected images and on early systems radiographers simply deleted unwanted images withno record being made. This is unethical practice. Even if this is not the case, rejected images
may simply reside in the system until they are removed to free up space.
(68) Reject and retake analysis should be included as part of the QA programme and enacted
through the quality management system (ICRP, 2022). Data should be collected regularly andanalysed on a monthly basis. Reject rates should be calculated and documented by body part andfacility location, and education/training or corrective action taken if rejected image rates areabove a predetermined threshold or start to rise. Rejects should be reviewed as a collaborative
task with radiologists and radiographers, and reasons highlighted as this can be a powerful selfassessment tool to enable and encourage improvement in practice.

865

2.4. Factors to consider in optimisation

866(69) The various factors, termed actions, that can influence digital radiography dose and867 quality, many of which have already been mentioned, are brought together in Table 2.4. These868 actions which can increase or decrease patient dose, are based on Table 2.3 in ICRP (2004) but
869 extended to include a wider range of actions.
870

Table 2.4. Actions that can affect patient dose and image quality
ActionEffect on
dose

Influence on image quality
or diagnostic information

Increase mAs to reduce noise perception

Increase

Improvement in SNR

Increase mAs further to give significant reduction ofnoise (with detector saturation in some areas)

Increase

Deterioration, retakes

Use appropriate tube potential and establish correct
radiographic techniques for digital systems

Decrease

May change appearance ofimage (optimisation)

Increase kV and reduce mAs to maintain same noiselevel

Decrease

Decrease in contrast(process of optimisation)

Inclusion of 0.1 mm or 0.2 mm copper filter in beamwith increased mAs to maintain noise level

Decrease

Minimal effect, possible
increase in exposure time

Implementation of dose and image quality indicators(KAP, EI, DI) on the console of x-ray system or PACS

Decrease

Potential improvement,
potential decrease in retakes

871

26

DRAFT REPORT FOR CONSULTATION: DO NOT REFERENCE

Table 2.4. (continued)
ActionEffect on
dose

Influence on image quality
or diagnostic information

Reduction in number of images per procedure (e.g.,
avoiding the lumbosacral spine image)Decrease

Remains unchanged

Increase source to detector distance

Decrease

Improve geometry

Increase in size of x-ray tube focus

Unchanged Reduced spatial resolution,
decrease in exposure time

Decrease in size of x-ray tube focus

Unchanged Improved spatial resolution

Expose full DR image plate and crop image to required
anatomy (poor practice)

Increase

Loss of contrast due toscatter from other tissues

AEC system not set up for correct image receptor type or Increase orcalibration incorrect
decrease

Potential degradation

AEC system not used

Increase or
decrease

Degradation, retakes

AEC chambers not checked regularly

Increase or
decrease

Degradation, retakes

Use of CR storage-phosphor plates beyond therecommended lifetime

Increase

Loss of quality, retakes

Use of a grid with too high a grid ratio

Increase

Susceptibility to grid
misalignment faults

Use of a grid with too low a line density

Possibledecrease

Risk of aliasing artefacts

Use of virtual grid software

ReducePoorer image quality thanusing a grid

Deletion of image files at the viewing station orworkstation of apparently non-useful images

Possibleincrease

Loss of information thatmight be useful inreject/retake analysis

Poorly adjusted / optimised diagnostic monitor (e.g.,
insufficient brightness, contrast, or resolution)

Possibleincrease

Loss of information,
potential for repeats

Use of workstation with more facilities to visualise
images (window, level, inversion, magnification)

Potential
decrease

Obtain more informationfrom the same image anddecrease no. of repeats

Implementation of reject and retake analysis programme Decrease

Possible improvement

Problems in postprocessing: hardware, network, etc.
during archiving of images

Increase

Occasional loss of images orretakes

Loss of images in the network or the PACS due toimproper identification or other reasons

Increase

RetakesUse of incorrect post processing introducing false lesions Possibleor pathologies due to artefacts
increase

Loss of information andneed for retakes, potential
misdiagnosis

Availability of workstation for post processing (and forradiographers) to avoid some retakes

Improvement27

Decrease

DRAFT REPORT FOR CONSULTATION: DO NOT REFERENCE

Table 2.4. (continued)
ActionEffect on
dose

Influence on image quality
or diagnostic information

Allowing easy access to the PACS and teleradiology tolook at previous images

Decrease

Improvement

Use of alternative post processing option, which cansometimes avoid repetitions.

Decrease

Improvement

Inability to post process images stored in the PACS, sothat re-analysis of images is not possible

Potential
increase

Potential need for retakes872

2.5. Image Post processing

873
874
875
876

(70) CR workflow can be divided into exposure of the CR plate, the read-out process in the CR
reader, and erasure of the plate. The readout process has several components, exposure field recognition,
histogram analysis, and greyscale rendition (Fig. 2.6) (Seeram, 2019). For DR the image data isrecorded at the time of exposure, eliminating the readout step.

877
878
879

Fig. 2.6. The basic steps in processing of digital x-ray image (Colin Martin, University ofGlasgow)

880
881
882
883
884
885
886
887
888
889
890
891
892

(71) Manufacturers have proprietary post processing algorithms that include contrast
enhancement; spatial frequency or edge enhancement; and multi frequency enhancement inwhich different spatial frequencies are manipulated separately. CR systems have numerous preinstalled look-up tables (LUTs) linking grey levels to exposure for different anatomical regions(e.g., head, chest, etc.). The appropriate LUT must be selected before the image is delivered to
PACS for reading, and use of an inappropriate selection may lead to a poor quality image thathas little value for diagnostic purposes.
(72) Windowing is a key tool used for adjusting image visualisation (Seeram, 2019). The
window width (WW) is the width of the range of pixel intensities displayed in the image andthe window level (WL) is the mid-point of the range. The appearance of a DR image can be
improved (or more often, temporarily altered by the radiologist while reviewing the images forinterpretation) through adjustments of greyscale and use of WW/WL can be used to achieve
better diagnostic image quality in parts of the image with varying contrast (Fig. 2.7).

28

DRAFT REPORT FOR CONSULTATION: DO NOT REFERENCE

893
894
895
896
897
898

a
b
c
Fig. 2.7. Windowing adjustment example. Paediatric chest images in NICU (a) with a higher
mAs dose, and b) with a lower mAs dose, and c) where windowing has been used to improve
contrast of the lower dose image (Dean Pekarovic, University Medical Centre Ljubljana,
Slovenia).

899
900
901
902
903
904
905
906
907
908
909
910
911
912
913
914
915
916
917
918
919

(73) Before an image is archived, contrast and edge enhancement can be adjusted to achieve
better visibility of the required anatomy or pathology. Although these tools can improve an
image, they do not replace appropriate choice of the exposure parameters and well-adjusted
indication specific post-processing.
(74) Before setting up protocols it is important for the user to become familiar with image
post processing steps and how different algorithms, which are often vendor specific, affectimage quality. During the initial protocol implementation phase, the imaging ofanthropomorphic phantoms can help in fine tuning the post-processing tools prior to
introduction into clinical use. Radiographers, radiologists, and medical physicists should work
together to identify the most appropriate processing algorithms for reporting when a new
radiography system is commissioned. During protocol creation, different options for postprocessing should be investigated on clinical images when time is available on PACS for image
review. This will aid selection of the most appropriate LUT and can help to identify lower dose
options that will give a similar quality image. Fig. 2.8 shows the same patient with the same
exposure parameters and illustrates the effect of different post processing algorithms.
Optimised practices and imaging protocols should be harmonised throughout an organisation
with many devices.
(75) There are pitfalls in over application of post-processing which can highlight features in
the image that are not significant clinically. For example, if multi-frequency post-processing iscarried out on chest x-rays for patients in the supine position on a trauma mattress, the folds ofthe mattress may be enhanced and appear in the images suggesting an abnormality.

29

DRAFT REPORT FOR CONSULTATION: DO NOT REFERENCE

920
921
922
923

Fig. 2.8. Chest radiographs of the same patient with similar exposure parameters, on which
different post processing algorithms and lookup tables (LUTs) have been used. (Dean
Pekarovic, University Medical Centre Ljubljana, Slovenia).

924

2.6. Optimisation of the imaging workflow

925
926
927
928
929
930
931
932
933
934
935

(76) When changing technology in the clinical environment all team members should bemade aware what changes mean for the daily workflow and how to control image quality anddose. The Ten Steps to Help Manage Radiation Dose in Paediatric Digital Radiography
published by Image Gently provide a good starting point for auditing radiography performance,planning, and allocating the who, how, and when for each step (Image Gently, 2022a). The
roles and responsibilities for all team members should be clearly defined to enable them towork together to achieve the objective. The basic steps are discussed in detail in Section 5.2.1:(77) A Digital Radiography Safety Checklist is recommended by Image Gently, divided into
four steps including what should be considered in each step (Box 2.4) (Image Gently, 2022b).
The checklist is intended as a quality assurance and improvement tool to assist radiographersthat perform portable DR and to reinforce the safety practices.

936

30

DRAFT REPORT FOR CONSULTATION: DO NOT REFERENCE

937

Box 2.4. Safety steps to image and verify for your patient (adapted from Image Gently)
Prior to Starting the Exam
1. Patient name selected from the worklist
2. Patient properly identified (two-point verification)
3. Appropriateness of request checked
4. Explained the exam to patient/parent
5. Verified Last Menstrual Period/pregnancy status if appropriate
Image Capture During the Exam
1. Beam body part image receptor aligned, SID checked, use of grid determined
2. Patient positioned and body part measured, cassette positioned (CR only)
3. Beam collimated
4. Technical factors selected
5. Shielding and markers placed
6. Final adjustment of tube and settings made7. Breathing instructions given
8. Exposure taken
Image Critique Immediately After Exposure
1. Cassette transported to and processed in reader (CR only)
2. Images displayed and reviewed; identification confirmed
3. Image quality reviewed
4. Exposure indicator/index checked; deviation index compared to target exposure index
5. Image reprocessed or repeated as necessary
Following Completion of the Examination
1. Post-processing performed only if necessary
2. Exam verified and images archived to PACS for reporting938

2.7. Basic quality assurance (QA)

939
940
941
942
943
944
945

(78) Acceptance testing and commissioning are crucial to ensure equipment is performing
optimally. Before any imaging system is first used, an acceptance test should be performed toverify image quality, dose, and compliance with the manufacturer’s specifications (ICRP, 2022).
After commissioning, medical physicists and radiographers should work together to establish
a local QA and management programme involving QC and other tests on different componentsof the system with defined tolerances and frequencies for all tests performed (IPEM, 2010;
AAPM, 2006, 2015).

946
947
31

DRAFT REPORT FOR CONSULTATION: DO NOT REFERENCE

948

2.7.1. CR systems

949
950
951
952
953
954
955
956
957
958
959
960
961
962
963
964
965
966
967
968
969
970
971
972
973
974
975
976
977
978
979
980
981

(79) The acceptance test for a CR reader and cassettes should identify any areas ofknowledge about which staff are uncertain, and dedicated training given to radiographers, aboutparameters used. Detailed QC testing is necessary to monitor the system performance, together
with defined tolerances and frequencies for all tests performed (AAPM, 2006; Walsh et al.
2008; IPEM, 2010). CR plates and the CR reader in every x-ray room should be checked, anda system of daily reporting of any differences in the imaging chain, which should be
investigated immediately. CR plates that have not been in use for more than 24 hours shouldbe erased before use. There are two types of erasing, the fast one is used on a daily basis, but
periodically a deep erase on all plates is recommended.
(80) Any cassette that has not been used for some time should be cleaned with a dedicatedcleaning fluid before being inserted into the CR reader. Too frequent and inappropriate cleaningof the screens can discolour the phosphor and create artefacts on the images. CR plates are notwaterproof and inappropriate cleaning of the cassette housing after use with a fluid can lead topermanent damage to the phosphor plate.
(81) CR plates can be damaged during the readout process by dust or particles of wet plaster(from patient castes). When artefacts on CR plates are recorded during QC tests, it is notnecessary to withdraw the CR plate from use. If they are near the edge and should not jeopardisethe diagnostic quality of the image, it is enough to inform radiographers of the exact positionof the artefact and keep a record, identifying the affected plates. A QC radiographer might
dedicate a plate for use only for pelvic or abdominal imaging and instruct other radiographers
to avoid paediatric or adult chest imaging where artefacts will be more visible. This can extend
the lifetime of a CR plate which can be important if funds are limited.
(82) The exposure index for CR plates is linked to the SNR performance and this will
deteriorate gradually over time and so cassettes need to be replaced. If a department hascassettes with a range in age or use, there is likely to be a range in EI values, which will beapparent when the EI is monitored. When new CR plates are introduced, they should be put
through a quick and simple acceptance test to inspect and check the plate quality.
(83) QC is achieved through exposures of test objects or phantoms, containing usuallysimple patterns, to assess the whole imaging chain (EC, 2004; ICRP, 2022). Somemanufacturers provide dedicated QC software with phantoms, and the phantoms, measuring
devices, and automated QC software should be requested at purchase. QC software can enableassessments to be carried out in shorter times and record images and tables of data
automatically.

982

2.7.2. DR systems

983
984
985
986
987
988

(84) Performance measurements for DR image receptors are similar to those for CR plates.
A simple QC test prepared in collaboration with medical physicists can be performed daily andaccording to a pre-installed QC protocol. Simple QC tests and established baseline values canprovide an effective tool for system inspection on a daily basis, and checking and controlling
performance of different components of the system, such as AEC performance, tube output,
and detector homogeneity (AAPM, 2006).

989

2.8. Approaches to Optimisation

990
991

(85) Digital radiography offers more flexibility in exposure level, giving the potential forimages to be obtained with lower exposures, and enabling levels to be adapted to the diagnostic
32

DRAFT REPORT FOR CONSULTATION: DO NOT REFERENCE

992
993
994
995
996
997
998

requirements of particular examinations. However, this capability is often not considered andstandard exposure levels are widely used. Radiology facilities should therefore implement
continual development of protocols and harmonisation across all the departments or facilities
within the organisation in order to achieve higher levels of optimisation. Box 2.5 sets out someof the arrangements that might be expected to be in place for x-ray facilities at different levels.
Facilities in level D, that have not yet achieved basic optimisation, should aim to put in place
the arrangements under level C as the first step.
Box 2.5. Arrangements that should be in place for facilities at different levels of
optimisation, together with aims that would be pursued.
C: Basic•••

Established protocols with appropriate tube potential and mAs settings for all common
examinations
Perform regular QC/QA tests on all digital x-ray units and CR readersRadiographers have received comprehensive training and receive further update training
whenever new units or features are implemented

B: Intermediate
•
•
•
•
•
•
•

Radiographers have access to diagnostic quality workstations
Full range of protocols established based on specific clinical indications
Image quality / exposure levels in protocols identified as low, medium or high based onclinical indication
Exposure index values recommended for a wide range of examinations and monitored
regularly.
Continual development of protocols through regular radiographer / radiologist / medical
physicist communication
A quality management system is implemented to maintain performance levels
Reject and repeat analysis programme implemented

A: Advanced
•
•
•
•

•
•

Unified guidelines for clinical indication-specific examination protocols throughout
organisation
Utilisation of dose monitoring system for an organisation wide on-line monitoring ofpatient exposures and analysis of exposure parameters for optimisation
Standard, objective and ongoing processes for evaluating optimisation undertaken withdefined timelines
Development of objective and quantitative image quality metrics based on diagnostic
image quality criteria. Establishment of more comprehensive and consistent optimisation
based on this.
Use of anthropomorphic phantoms in optimisation.
Use of a generic approach, whereby the optimisation of exposure and post-processing
parameters, and related exposure index values could be included in the commissioningof new equipment.

999
33

DRAFT REPORT FOR CONSULTATION: DO NOT REFERENCE

3. INTERVENTIONAL AND OTHER FLUOROSCOPIC
PROCEDURES

1000
1001
1002
1003
1004
1005

(86) Key messages in this section:• Fluoroscopy is an interactive imaging procedure requiring proper use of equipment
features to perform the clinical task with the lowest possible radiation dose to thepatient and staff members.

1006
1007
1008

•

Optimisation requires appropriate selection and configuration of a complex set ofdesign features for the fluoroscopy system, tailored to the clinical tasks and required
level of image quality.

1009
1010
1011
1012

•

Protocols should be configured to give the required image quality and dose saving
needs for the clinical task. This includes the settings for the automatic dose rate
control (ADRC) system and other programmes for which acquisition parameters arechanging.

1013
1014
1015

•

Quality control (QC) programmes should be established to evaluate performance of
all exposure modes relating to selection of options that are optimal for specificimaging tasks.

1016
1017
1018
1019
1020

•

For complex interventional procedures, where there is a risk of skin injury,
cumulated dose quantities should be monitored during the procedure and recordedon completion. Appropriate trigger levels should be pre-defined for patient follow
up and management of tissue reactions. Exposure, from previous and potential
future procedures should also be considered.

1021
1022
1023
1024

•

Optimisation should consider radiation risk in conjunction with other non-radiation
related risks, e.g., use of contrast media, medications, sedation/anaesthesia, etc. The
proper timing of procedure and its optimal performance should be carefullybalanced for each individual patient and each clinical situation.

1025
1026
1027

•

X-ray beam projection and angulation with C-arm systems should be selected toprovide the required anatomical visualisation, bearing in mind that steep
angulations increase patient dose.

1028
1029
1030
1031

•

The use of low fluoroscopic pulse rates and pulse lengths, proper collimation andchanging the angulation and beam entry to reduce the possibility of overlap ofradiation fields from different projections, should be used to keep peak skin dose
below the threshold for skin injury.

1032
1033
1034

•

Components of the QA programme dealing with dose management should be put inplace to enable the optimisation process to progress and a core team established topromote optimisation through review of common fluoroscopic procedures.

1035

3.1. The evolution of fluoroscopic techniques

1036
1037
1038
1039
1040
1041

(87) Fluoroscopy produces dynamic images of structures and organs in real time, whichallow for its application for diagnosis and for navigation of instruments to perform different
surgical, minimally invasive and interventional procedures.
(88) This section deals with optimisation of all aspects of the use of fluoroscopy, includinginterventional radiology and cardiology and digital subtraction imaging. It covers fluoroscopy
performed in the radiology department or other dedicated facilities, as well as use of mobile34

DRAFT REPORT FOR CONSULTATION: DO NOT REFERENCE

1042
1043
1044
1045
1046
1047
1048
1049
1050
1051
1052
1053
1054
1055
1056
1057
1058
1059
1060
1061
1062
1063
1064
1065
1066
1067
1068
1069
1070
1071
1072
1073
1074
1075
1076
1077
1078
1079
1080
1081
1082
1083
1084
1085
1086
1087
1088
1089
1090

fluoroscopy in operating theatres and hybrid rooms, and the application of cone beam CT
incorporated into fluoroscopy equipment.
(89) Since its discovery, significant advancements have been made in fluoroscopy
equipment and techniques, which have impacted their clinical use. Since the invention of the
x-ray image intensifier (II) and the television camera in the 1950s improvements in intensifier
technology and image displays, in parallel with developments in x-ray tubes and generators,
have enabled enhancement of image quality while allowing the radiation doses to patients tobe reduced substantially. This trend has continued with the introduction in 2000 of digitalsystems based on flat panel (FP) detectors which are currently widely available and continue
to develop (Balter, 2019).
(90) Fluoroscopy was initially a technique used only by radiologists in diagnosis, but thischanged with the development of fluoroscopically guided percutaneous procedures to its
current widescale use as the method of choice for complex interventions by many different
medical specialists (UNSCEAR, 2008, 2022). While the frequency of diagnostic fluoroscopy
studies (e.g., barium meal and urologic studies) has decreased, many being replaced by crosssectional (US, CT, MRI) and minimally invasive alternatives (endoscopy), thefluoroscopically-guided interventional (FGI) procedures have increased by type, number andcomplexity. The estimated annual total of about 24 million interventional radiology proceduresin the latest UNSCEAR report represents a sixfold increase from the 3.6 million procedures inthe earlier report, while the collective dose has risen by a factor of eight. The increased use isdue to their relatively low invasiveness and risk, faster recovery times, shorter hospital stays
and lower cost compared to surgery. However, FGI procedures are performed in a variety ofsettings and sometimes by clinicians with insufficient knowledge and awareness of radiation
exposure. This puts patients and staff members at increased risk, not only for long-term
stochastic effects, but also of tissue reactions such as skin injuries and cataract (ICRP, 2000b,
2010, 2013a; IAEA, 2010). It is critical that all clinicians receive appropriate education andpractical training before undertaking any FGI procedures. The optimisation task in fluoroscopic
imaging is far from trivial. It requires appropriate selection of a complex set of technicalparameters, tailored to the clinical task, and should start with the establishment of a core teamof radiologist, radiographer, and medical radiation physicist properly trained in fluoroscopy.
When FGI procedures involve clinicians and/or surgeons, nurses, and anaesthetists, they must
understand radiological protection principles of justification and optimisation and undergo both
initial education and ongoing training (ICRP, 2009, 2022; NCRP, 2010).
(91) Fluoroscopy is an interactive imaging procedure requiring proper use of equipment
features to perform the clinical task with the lowest possible radiation dose to the patient andstaff members. Optimisation requires appropriate selection and configuration of a complex setof design features for the fluoroscopy system, tailored to the clinical tasks and required levelof image quality.
(92) Optimisation in fluoroscopy comprises several equally important steps, which should
be appreciated and implemented in practice. These are;1) Appointing a multi-disciplinary team (medical physicist, radiographer andradiologist/interventionalist) to establish appropriate design features for selection of afluoroscopy system consistent with the intended clinical uses (Section 3.2).
2) Proper configuration and exposure setting optimisation at the time of commissioning of
the system, tailored to the clinical tasks and required image quality (Section 3.3).
3) Establishment of a Dose Management QA programme along with the core team toestablish and promote optimisation through reviews of common fluoroscopic procedures.
(Section 3.8)
4) Applying a comprehensive Dose Management QA programme, including equipment
35

DRAFT REPORT FOR CONSULTATION: DO NOT REFERENCE

1091
1092
1093
1094

maintenance and QC tests to verify the equipment performance (Sections 3.4, 3.5 and 3.7|).
5) Appropriate use of the available equipment features and settings by the operators, toperform the clinical task with minimum possible exposure to the patient and to the clinicalteam members. (see Sections 3.6 and 3.7)

1095
1096

3.2. Design features of modern fluoroscopy systems relevant to patient doseand image quality.

1097

3.2.1. Major equipment components
Box 3.1. Types of Fluoroscopy equipment
Conventional R/F systems combine fluoroscopy (F) and radiography. These systems havebeen used for a wide variety of diagnostic examinations such as barium contrast studies of
the upper and lower gastro-intestinal (GI) tract although many of these have now beensuperseded by other techniques. The systems are also used for contrast injections of theurinary tract, vascular and other catheter devices, percutaneous drains, and therapeuticinterventions that involve the GI, gastro-urinary, chest, musculoskeletal and vascularsystems. Equipment consists of a patient table that can be tilted from horizontal to a vertical
position to distribute the contrast through the organs or structures of interest. The system
most often has an x-ray tube fixed under the table, and a large field of view (FOV) image
receptor above the table, which can be moved by the operator closer or further from thepatient. A variation of the combined R/F system is the remote-control R/F system, whichfeatures the opposite configuration of the x-ray tube above the table, and the image receptor
fixed under the table.
“C-arm” geometry systems are either fixed or mobile, allow for an easy change of the
projection angle adapted to the clinical needs. This configuration enables alignment of thecentral radiation beam with the centre of the radiation detector, regardless of thedisplacements that are performed during the clinical procedures. Mobile systems are often
used in theatres to be positioned next to the operating table, and images are used to navigate
a variety of treatment procedures, including minimally invasive procedures in orthopaedic
surgery, traumatology, general surgery, urology, gastroenterology, pacemaker and vascularaccess placement, etc. The C-arm systems have an x-ray tube at a fixed distance from thecentre of rotation (isocentre), relatively small FOV and short source to image distance. They
provide for flexible programme set up, pulsed fluoroscopy and spectral filter options.
Modern systems have the capability to acquire 3D image data and operate as cone-beam CTs.
Angiography systems also use a “C-arm” configuration, but they are often fixed andnormally incorporate features linked to the specific requirements of the more complex
diagnostic and therapeutic vascular and non-vascular interventional procedures. The
procedure requirements include longer fluoroscopy times, many acquisition (digital cine)series, many different angulations and views, extensive use of iodine-based contrast media,
use of guidewires and small devices, and the need for high spatial and temporal resolution.
Such units have powerful x-ray tubes, many fluoroscopy modes, variable frame-rates,
comprehensive automatic dose rate control (ADRC) systems and spectral filters. They also
allow for digital subtraction, road mapping and other post-processing capabilities.
Angiography systems typically also have 3D imaging capabilities extending their use tocone-beam CT acquisitions.
36

DRAFT REPORT FOR CONSULTATION: DO NOT REFERENCE

1098
1099
1100
1101
1102
1103
1104
1105
1106
1107
1108
1109
1110
1111
1112
1113
1114
1115
1116
1117
1118
1119
1120
1121
1122
1123
1124
1125
1126
1127
1128
1129
1130

(93) Fluoroscopy systems are manufactured in a variety of configurations allowing
optimisation of the system for the intended clinical tasks. The main configurations are a)conventional fluoroscopy systems with the additional capability to perform radiography, b) Carm systems and c) angiography systems (see Box 3.1 for further details). Appropriate
selection of the design features of a fluoroscopy system consistent with the intended clinicaluses is imperative if the Dose Management QA programme is to function as intended.
(94) A fluoroscopy imaging system generally includes a high-power generator, a high heat
capacity x-ray tube, and an image receptor, which could be either an image intensifier (II), ora flat panel (FP) detector. It also commonly includes a filter (Box 2.3), field restriction device(collimator) attached to the tube housing, and an anti-scatter grid attached to the entrance
surface of the image receptor, the role of which is to remove the scatter radiation and improveimage contrast (at the price of increased dose). The anti-scatter grid should be easily removable,
especially when the system is to be used for paediatric patients.
(95) Image receptors for both IIs and FPs are available in a range of sizes, varying fromabout 10–15 cm up to 40 cm depending on the intended clinical application.
(96) Fluoroscopy equipment can be operated in either fluoroscopy or radiography mode.
Most applications involve the use of both modes, to combine the good temporal resolution offluoroscopy, with the higher signal to noise ratio (SNR) and recording/ archiving capabilities
of radiography. In fluoroscopy mode, the images are viewed in real time but not always
recorded. In the radiography mode (also called “fluorography” in older systems) the images
are recorded as single (spot) images, a number of images (acquisition), or as a sequence ofserial images (also called “cine”) that can be viewed after the procedure. Patient doses per
image frame in radiography mode can be orders of magnitude higher than those in fluoroscopy
mode. With larger and less expensive storage becoming available, some facilities are choosing
to capture and store fluoroscopy mode imaging especially for paediatric cases in order toachieve dose savings.
(97) Fluoroscopy/radiography mode is selected on the console, or by the operator at the startof or during the study, and based on the protocols defined in the equipment. The tube current
in radiography mode is tens to a hundred times higher than in fluoroscopy, to provide high SNR
in a short exposure time. Operators need to be aware of the difference between the modes,
including the associated dose rate. The use of radiography for recording/archiving, and thenumber of recorded images need to be limited to the minimum necessary for the clinical task.

1131

3.2.2. System features determining x-ray beam quality and exposure levels

1132
1133
1134
1135
1136
1137
1138
1139
1140
1141
1142
1143
1144

(98) Modern fluoroscopy systems operate in pulsed fluoroscopy and other acquisition modes
with several pulse rate options. See Box 3.2 for further information. The lowest pulse rateshould be used to obtain images of acceptable quality for the imaging task. Lowering the pulse
rate however reduces temporal resolution that might be unacceptable for the most rapidly
moving organs (e.g., heart or barium video swallowing study), which might require higher
pulse rates with or without added magnification.
(99) Modern fluoroscopy systems are also equipped with beam spectrum shaping filters(spectral filtration) usually made of aluminium and/or copper, positioned at the exit of the xray tube. Their role is to absorb the low-energy photons thus reducing the absorbed dose to skinand superficial tissues, but also to increase image contrast by shaping the x-ray spectrum tomatch the k-absorption edge of barium (at 33.44 keV) or iodine (at 33.17 keV). Other filter
materials like gold and tantalum are also used to modify the spectrum.
(100) In addition to the beam shaping filters, many fluoroscopy systems have semi37

DRAFT REPORT FOR CONSULTATION: DO NOT REFERENCE

1145
1146
1147
1148

transparent “wedge” filters that can be moved by the operator to selected regions of the FOV,
in order to compensate for the lower object attenuation in a region, thus keeping the image
brightness constant and maintaining image quality.
Box 3.2. Pulsed fluoroscopy
Modern fluoroscopy systems operate in pulsed fluoroscopy and other acquisition modes withseveral pulse rate options. Pulsed means that the x-rays with pulse widths between 2 and 15
ms are emitted at typically 3, 7.5, 15 or 30 pulses per second (pps) (user selectable), but alarger range of options may be available in modern equipment. The gap between pulses on
the display is filled with the last acquired image. The use of short pulses of the x-ray beaminstead of continuous emission results in sharper images due to the reduced motion blur. At
high pulse rates, typically 30 pps that are similar to the frame rate of the display, observers
perceive the rapid sequence of image frames as a continuous motion due to the lag in thehuman visual system. At pulse rates of 30 pps, the entrance surface air kerma (ESAK) rate
at the patient surface may be similar to that with continuous fluoroscopy. The figure shows
the variation of the ESAK rate for different pulsed fluoroscopy modes. The expected 50%
dose reduction when changing from 30 to 15 pps may not occur as the relationship between
pulse rate and radiation exposure is variable especially among older systems. This resultsfrom the fact that the generator may increase the tube current automatically to maintain aconstant SNR. Real dose reductions of around 22% have been reported in the past (Aufrichtig
et al., 1994; Mahesh, 2001).

Fig. Effect of pulsed fluoroscopy on patient entrance surface air kerma rate for constant SNR.
1149
1150
1151
1152
1153
1154
1155
1156
1157

(101) All fluoroscopy systems are equipped with a collimator device to limit the geometricextent of the x-ray field, which might have circular and/or rectangular shape, matching theshape of the image receptor. The automatic collimator system ensures that the x-ray field isalways aligned to the selected field of view, and never extends beyond the image receptor limits.
In addition to the automatic collimation, dual-shape collimators are typically available,
incorporating both circular and rectangular shutters to be used to modify the field forcollimation around areas of interest. Limitation of the field size to the region of interest isimportant since it limits the dose to the patient and reduces scatter radiation, thus improving
image contrast and also reducing the radiation scattered to staff present in the room.
38

DRAFT REPORT FOR CONSULTATION: DO NOT REFERENCE

1158
1159
1160
1161
1162
1163
1164
1165
1166
1167
1168
1169
1170
1171
1172
1173
1174
1175
1176
1177
1178
1179
1180
1181
1182
1183
1184
1185
1186

(102) Modern fluoroscopy systems feature a last image hold (LIH) capability, which is thecapture and display of the last acquired frame. Some systems incorporate a Last Series Hold
(LSH) feature that can even replace digital runs (Radvany and Mahesh, 2015). These are usefulfeatures that reduce the fluoroscopy exposure time and thus patient exposure, by viewing theimage details without exposing the patient. The images remain only until the next fluoroscopy
exposure (IEC, 2019).
(103) Modern fluoroscopy systems have automatic positioning systems, which reduce theamount of fluoroscopy time required to properly position the system for various imaging
procedures. Also, a “virtual collimator” is available which allows the operator to manipulate
collimator blades while using LIH, thus eliminating the need for fluoroscopy and reducing
radiation dose (NEMA, 2016).
(104) Fluoroscopy system incorporates an automatic dose rate control (ADRC) sometimes
referred to as automatic brightness control (ABC). This device automatically adjusts exposure
parameters and the incident air kerma (IAK) rate to the image receptor, to deliver a constantsignal intensity at the image receptor, resulting in constant image brightness and SNR at thedisplay despite body habitus. Different ADRC programmes are available to optimise theimaging for different anatomical regions, so the operator should be aware of the options andselect the mode appropriate for the imaging task. See Box 3.3 for an example.
(105) Fluoroscopy systems feature different electronic magnifications (also referred to as“zoom” or “mag”), which are used to magnify a portion of the image at improved high contrast
resolution. In II-based systems, this is done by changing the electronic focusing inside the II,
which results in an increased IAK rate at the image receptor that is inversely proportional tothe area of the FOV. Thus, doubling the electronic magnification multiplies the IAK by a factorof 4. Flat panel-based systems also increase the rate as the image is magnified in response tochanges in the image matrix size. However, the increase in IAK rate with magnification is lesspronounced, as the spatial resolution in a FP system is theoretically independent of the FOV.
In practice, the increase of the IAK rate with FOV is vendor dependent, commonly reciprocallyrelated to FOV. The actual relationship should be checked at commissioning to ensure that it is
as expected (Section 3.3).

1187

3.2.3. Image display considerations

1188
1189
1190
1191
1192
1193
1194
1195
1196
1197

(106) LIH and LSH features should be used whenever possible (Section 3.2.2). Some systems
allow users to store and replay at least 300 frames of the most recent fluoroscopic-imaging
sequence, which should always be the preferred options to reduce patient exposure, instead ofrecording radiographic images or a cine-series (NEMA 2016; IEC 2019).
(107) Image display monitors have an important role in the visual perception of the images
and therefore an indirect impact on the patient and consequently staff dose, especially influoroscopy guided procedures that require the operator to be close to the patient. Using large(e.g., 60”) monitors helps lower patient dose by reducing the need for magnification mode, thus
reducing the patient and staff doses. This also allows the operator to see small vessels fromlarger distances thus reducing the scatter dose reaching the eyes (Balter, 2019).

1198

3.3. Exposure configuration and optimisation during commissioning

1199

3.3.1. Imaging features and requirements

1200
1201

(108) Fluoroscopy systems provide a selection of pre-configured examinations and patient
specific technical sets (Balter, 2019). Each configuration comprises of a set of exposure
39DRAFT REPORT FOR CONSULTATION: DO NOT REFERENCE

1202
1203
1204
1205

technique factors and image processing parameters, which are programmable and adjustable tothe local practice and user preferences by a vendor representative (application specialist) or a
local authenticated user, in collaboration with the hospital medical physicists and experienced
representatives of the clinical staff (the core team).
Box 3.3. Example of automatic dose rate control (ADRC) programming
The selection of exposure factors (tube voltage and tube current) follows predetermined
curves that are stored in the generator, adjusted for each equipment model and manufacturer(see figure below). While the changeable exposure factors are typically the tube voltage andthe tube current, the ADRCs in more advanced systems include the filtration added to thetube, the pulse width and the focal spot size. The fluoroscopy system allows for operatorselectable fluoroscopy modes which use different curves, including a standard (normal), lowdose and high dose (high contrast) curves. As patient attenuation increases the incident air
kerma rate at the patient increases, while that at the image receptor does not vary. However,the IAK rate at the image receptor normally increases when changing from low-dose to highdose mode to provide a higher level of image quality.
The ADRC algorithms adjust the exposure factors to maintain the patient ESAK rate forfluoroscopy within levels recommended in regulatory guidance which normally leads todegradation of image quality for high attenuation objects such as obese patients, lateral or
oblique projections, or thicker body parts.

Fig. Example kV vs. mA curves for fluoroscopic exposure modes suitable for different
imaging tasks. When the limiting entrance surface air kerma rates at the patient are reached,
there are sharp discontinuities as the tube potential is increased and the mA reduced to avoid
exceeding the limiting ESAK rate. (Colin Martin, University of Glasgow)
40

DRAFT REPORT FOR CONSULTATION: DO NOT REFERENCE

1206
1207
1208
1209
1210
1211
1212
1213
1214
1215
1216
1217
1218
1219
1220
1221
1222
1223
1224
1225
1226
1227
1228
1229
1230

(109) Based on the different image quality requirements for different clinical tasks, protocols
differ for application: e.g., cardiac, neuro, vascular, paediatric, and also for different acquisition
techniques such as digital subtraction angiography (DSA). The configuration parameters foreach of these protocols are hidden from users and can only be modified by a user with elevatedaccess rights to the equipment. Testing and adjustment of these parameters during thecommissioning is of great importance. It does require however clear understanding of thesystem features, functions, programme architecture, as well as the clinical requirements andoperators’ preferences.
(110) Protocol configuration should include consideration of the use of an anti-scatter grid,
lower tube voltage, optimal use of collimation and wedge filters, as well as contrastenhancement during image processing. There may sometimes be a clinical need to reduce noisethat may require an increase in photon flux using a higher mA. Close attention should be paid
to collimation to reduce scatter. For improving visual contrast perception, extra bright monitorsand optimal viewing distance are also recommended.
(111) For example, a clinical study requiring visualisation of high-resolution images (e.g.,
small vessels, fine instruments, etc.) requires small focal spot size; smaller source to image
detector distance and object to detector distance, small detector pixel size and large matrix,
magnification, and good visualisation conditions with large monitors that have high brightnesslevels. Modern post-processing using fast image enhancement algorithms such as
multifrequency processing improves the visualisation of contrast structures significantly. Suchhigh resolution dynamic imaging requires higher pulse rates (15 or 30 pps) with smaller pulse
widths, as well as special image processing techniques.
(112) The facility core team should create a variety of selectable pre-defined study protocols
and acquisition programmes for the procedures commonly performed with a particularfluoroscopy equipment.

1231

3.3.2. Optimisation of acquisition protocols during commissioning

1232
1233
1234
1235
1236
1237
1238
1239
1240
1241
1242
1243
1244
1245
1246
1247
1248
1249
1250
1251
1252

(113) During equipment commissioning, medical physicists should check whether acceptablevalues have been set for the default acquisition programmes and necessary adjustments should
be made in collaboration with the equipment vendor representative and clinical staff. This
includes confirmation of equipment function, checking baseline values of equipment
performance in terms of image quality and dose parameters, using standard phantoms and test
objects, and representing a range of patient sizes (AAPM, 2012; Stevens, 2021; Lin et al., 2022).
An important task at the stage of commissioning is to optimise the system for the clinical tasks
and set these modes as defaults.
(114) Protocol configuration includes proper adjustment of settings customised to therequired image quality and dose saving needs for the clinical task. Protocols should be
configured to give the required image quality and dose saving needs for the clinical task. This
includes the settings for the ADRC system and other programmes for which acquisition
parameters are changing.
(115) During the system commissioning and configuration, ADRC settings for different
modes and anatomical/clinical programmes should be tested and adjusted; baseline values
should be set for the IAK rate at the image receptor, as well as the patient’s ESAK rate (AAPM,
2012; IPEM 2021). Note that there is only an indirect correlation between the image receptor
IAK rate and the patient ESAK rate (AAPM, 2012).
(116) One of the most challenging tasks during the system configuration is to set appropriate
values of IAK rate at the image receptor in fluoroscopy and radiography modes, for different
fluoroscopy dose modes, pulse rates and FOVs (AAPM, 2012; Jones et al., 2014, Stevens,
41

DRAFT REPORT FOR CONSULTATION: DO NOT REFERENCE

1253
1254
1255
1256

2021).
(117) The changes in the IAK rate with the fluoroscopy pulse rate and FOV need to be tested
during commissioning, and properly adjusted to meet the image quality requirements for thedifferent clinical indications and patient types.

1257

3.4. Establishing equipment performance and QC programme

1258
1259
1260
1261
1262
1263
1264
1265
1266

(118) Quality control (QC) programmes should be established to evaluate performance of all
exposure modes relating to selection of options that are optimal for specific imaging tasks. The
requirements of QC programmes are discussed in part 1 of this publication. QC is an essential
component of the Dose Management QA programme. Fluoroscopy equipment QC requires awide variety of tests to be performed with different frequency as described in dedicatedguidance publications, and briefly summarised in Table 3.1 (AAPM, 2001, 2012; IPEM 2005,
2010; EC, 2012; IEC, 2019). Where appropriate, testing should be performed for all dose/image
quality modes and possible magnifications and image acquisition (fluoroscopy andradiography).

1267

Table 3.1. Summary of QC tests for a fluoroscopy system
Elements of QC programme

Parameters to be measured

X-ray source assembly

Accuracy and reproducibility of the tube voltage
Half- value- layer (HVL)
Reproducibility and linearity of the tube output
Tube leakage

Collimation and radiation fieldalignment

Alignment and collimation of the radiation field to the image
receptor

ADRC settings and performance

IAK rate at the image receptor and patient ESAK rate for mostcommonly used modes and programmes

Integrated radiation dose
displays

Verification of calibration of KAP meter

Image quality

Noise level

Verification of displayed KAP and reference air kerma
Correction factors for use with RDSR when function is available
Low contrast detectability
High contrast detectability
Image distortion and artefacts

Cone Beam CT (CBCT) mode if
available (EFOMP-ESTROIAEA, 2019).
1268
1269
1270
1271
1272
1273
1274
1275

Dose parameters
Geometry characteristics
Image quality(119) Currently test objects used for QC tests are not particularly representative of body
habitus or the conditions encountered in the clinical setting. More realistic test objects thatenable task-based model observer evaluations of system imaging performance may soon
become available. It is anticipated that vendors of fluoroscopy equipment will provide a User
Quality Control Mode (UQCM) for interventional procedures which will allow for an easierand reproducible QC process without vendor involvement and with clinical processing disabled(NEMA, 2018; IEC, 2019). This mode will allow for more comprehensive physical tests to be
introduced in the routine QC programme.
42

DRAFT REPORT FOR CONSULTATION: DO NOT REFERENCE

1276

3.5. Patient dose monitoring and dose audits

1277
1278
1279
1280
1281
1282
1283
1284
1285
1286
1287
1288
1289
1290

(120) Reliable dosimetry of patients is essential for achieving optimisation. In fluoroscopy,
dose management is concerned with both stochastic effects and tissue reactions. Thus, modern
equipment provides dose data on the operator’s monitor that includes the KAP rate and incident
air-kerma rate at the patient entrance reference point, as well as their cumulated values (IEC,
2019).
(121) All available dosimetry information, along with images and other procedure-related
information should be recorded and stored at the level of modality in a standard format. Modern
equipment should be able to record these data electronically in a Radiation Dose Structured
Report (RDSR) (see Annex B).
(122) The Dose Management QA programme should include provision for local audits ofpatient dose quantities for which local or national diagnostic reference levels (DRLs) areestablished and for providing patient management/follow-up (ICRP, 2022). However, DRLs
are much more challenging to implement for FGI examinations than in conventional
fluoroscopy. See Box 3.4 for further explanation.
Box 3.4. DRLs in FGI procedures
Whilst DRLs are very useful for diagnostic examinations they are much more challenging to
implement or interpret in the case of FGI procedures because a) such procedures are bydefinition therapeutic, not diagnostic and b) there is a wide distribution of patient doses forany given examination. Therapeutic interventions vary by severity, complexity and site andare therefore more or less unique. As a result, interventional procedures demonstrate
substantial variability in the amount of radiation used for individual cases as a result of
patient, operator and equipment factors. (ICRP, 2017; COMARE, 2021).
ICRP recommends that even though interventional procedures are therapeutic, the term DRL
is retained for use in IR since their purpose is to provide a tool for optimisation and theadoption of a different nomenclature is likely to result in confusion. (ICRP, 2017) The
publication does however recommend that DRLs for interventional procedures should be
developed differently from those for diagnostic procedures. One possible approach is to try
and determine the ‘complexity’ of a procedure; another is to utilise the concept of Advisory
Data sets. Both are difficult to implement in practice.
Kerma-area product (KAP, PKA) is the preferred metric for DRLs. Other quantities that canpossibly be used are reference air kerma (Ka,r) (IEC, 2020) (also referred to as the cumulative
air kerma (CAK) at the patient entrance reference point, fluoroscopy time and the number ofradiographic images obtained as part of the procedure. If Ka,r is available, it can be used toprovide additional information to assist optimisation. For instance, a comparison of PKA andKa,r values can be used to judge the adequacy of beam collimation.
The number of patients to include in the dose audit survey depends on the complexity of theprocedure and the resources. Larger numbers of patients may be needed for FGI
interventional procedures, and preferably the data from all interventional procedures
performed (not just from a limited sample) should be collated.
For further information on DRLs, see ICRP (2017).

1291

43

DRAFT REPORT FOR CONSULTATION: DO NOT REFERENCE

1292

3.6. Skin dose monitoring and alert levels

1293
1294
1295
1296
1297
1298
1299
1300

(123) In some complex interventional procedures, patient skin and even the underlying bone
structures may receive high radiation doses that exceed the dose threshold for tissue reaction(ICRP, 2000b, 2012; Balter et al., 2010; NCRP, 2010; Jaschke et al., 2017). Prevention of
injuries and minimising the adverse effects for patients is possible in most cases ifinterventional specialists work with attention and apply the proper techniques. Dose monitoringand patient follow-up are essential for management of tissue reactions. The best way to predictpossible radiation effects is to estimate the distribution of absorbed doses on the surface of thepatient´s skin and the peak skin dose (PSD) value (Box 3.5).

1301
1302
1303
1304
1305
1306
1307
1308
1309
1310
1311
1312
1313
1314
1315
1316
1317
1318
1319
1320
1321
1322
1323
1324
1325
1326
1327
1328
1329
1330
1331
1332
1333
1334
1335
1336
1337
1338

(124) Estimation of PSD will require assessment and analysis by the qualified medical
physicist. Ideally, this information should be available in real time during the procedure, andnotification provided to the operator to modify the technique in order to avoid skin dose
exceeding the threshold for tissue reaction. Alternatively, post-procedure feedback should be
provided and proper follow-up programmes established in interventional facilities.
(125) Procedures associated with radiation doses that might involve a risk of tissue reactions
include: embolisation (including chemoembolisation); stent and stent graft placement;
percutaneous coronary intervention, radiofrequency ablation; transjugular intrahepatic
portosystemic shunt creation or revision; endovascular aneurysm repair; or stent placement;complex biliary intervention, complex, multilevel vertebral augmentation procedures(including vertebroplasty and kyphoplasty) (ICRP, 2000b, 2010, 2013a; Stecker et al., 2009;
Jaschke, et al., 2020).
(126) PSD can be measured directly using different types of dosimeters or calculated frommeasure dose quantities. If that is not possible, it can be estimated from Ka,r or PKA. See Box
3.5 for further details.
(127) The Dose Management QA programme should include an element in which dose values
are monitored throughout the clinical procedure. The cumulated values should be recorded in
the patient medical record after the procedure and kept in the departmental records for review.
The operator should be notified when a dose parameter exceeds a pre-defined alert level during
the procedure. This does not mean that the procedure should be interrupted, but having been
notified about a high dose, the operator might be able to modify some technique elements using
options discussed below in Section 3.7.2, and consequently avoid the threshold for tissue
reactions. Alerts should preferably pop-up automatically, but if no means exist for setting
automatic alerts in the fluoroscopy system, the responsibility for monitoring dose values andnotifying the operator should be delegated to an appropriate staff member (Stecker et al, 2009,
Jaschke, et al., 2020). Suggested alert levels are summarised in Table 3.2 (Stecker et al., 2009;
NCRP, 2010). Rarely will it be necessary for a procedure to be stopped due solely to radiationdose, as this will incur a risk with no benefit to the patient. When appropriate, complex clinicalprocedures may be planned in a staged fashion, with multiple sessions separated by 8–10 weeks,
so that the dose to the skin is fractionated to reduce the likelihood of tissue reactions (Fisher etal., 2021).
(128) Post-procedure dose notification should be provided to the operator in case any of thereported dose values reach the pre-defined trigger levels for patient follow and management oftissue reactions. Table 3.2 shows trigger levels as suggested by the international web-based
voluntary and anonymous reporting system for fluoroscopy guided interventional procedures
SAFRAD (SAFety in RADiological procedures) of the IAEA. SAFRAD aims to collectinformation about procedures exceeding trigger levels and define more realistic trigger dose
indicators for different types of interventional procedure.
44

DRAFT REPORT FOR CONSULTATION: DO NOT REFERENCE

Box 3.5. Measurement, calculation, and estimation of PSD
Measurement: PSD can be estimated directly using different types of dosimeters, attachedto the entrance surface of the patient: thermoluminescence detectors, slow x-ray films,
radiochromic films, MOSFET radiation sensors, or scintillation dosimeters (Vano et al.,1997, 2001; Balter et al., 2002; Fletcher et al., 2002). Radiochromic films have proven to bea suitable solution to measure PSD with an uncertainty of around 15–20%, if care is taken
for proper calibration and measurement conditions (McCabe et al., 2011; Farah et al., 2015;
Greffier et al., 2017). This method is however time-consuming and expensive and cannot beapplied routinely. Practically, radiochromic film is sometimes used in cases when a complex
or prolonged procedure is anticipated (Stecker, 2009).
Calculation: PSD can be calculated from the measured dose quantities, geometry andexposure parameters taken from the RDSR data or other types of dose report and a Medical
Physicist should be involved in making such assessments (Jones et al., 2011, 2012). The
accuracy of the method depends on several factors, including the calibration accuracy of
dosimetric equipment, accuracy of information reported in the DICOM header andproprietary dose reports, accuracy of dose quantities (PKA and Ka,r) measured by the medical
physicist, and procedural factors such as rotation of the C-arm during a fluoroscopicallyguided procedure (Jones et al., 2012). There are several software products for skin dose
calculations, most based on the methodology proposed by Jones and Pasciak (Jones et al.,2011, 2012), and a few use Monte Carlo simulations of the photon transport. A review
performed under the European VERDIC project found considerable differences in theimplementation and strong heterogeneities in encoding examination related parameters in
the RDSR and the export of DICOM fields (Malchair et al., 2018). Most of these software
products provide post-procedure 2D or 3D skin dose maps based on an anthropomorphic
phantom library matched to a patient body size and shape (Lee et al., 2010). There aredevelopments to provide real-time information on skin dose and dose rate during FGI
procedures, with visual presentation of the cumulative results of colour skin dose mapped
onto an anthropomorphic model (Bednarek et al., 2011; Johnson et al., 2011; Bordier et al.,2015; Rana et al., 2016). The real-time feedback has been demonstrated to have a significant
positive effect on the operator awareness and for enhancing patient safety during FGI
procedures (Wilson et al., 2016; Ichimoto et al., 2018)
Estimation: If no means of measurement of PSD is available, reference air kerma, Ka,r and
PKA can be monitored, and alerts set for these quantities. Ka,r is the best predictor of the
maximum skin dose, but it does not always correlate well with PSD, depending on theprocedure type, specific protocol, use of different projections, operator experience, etc.
Correlation of PSD with the cumulated KAP is weaker although still good for someprocedures, especially if projection does not change during the procedure. However, since
the correlation depends on beam area, it is dependent on the procedure (Neil et al., 2010).
Fluoroscopy time and number of acquired images are poor predictors of skin injuries (Balter
et al., 2002; Pasquino et al., 2018). The correlation between PSD and dose indicators should
be assessed for each equipment and procedure type.
1339
1340

45

DRAFT REPORT FOR CONSULTATION: DO NOT REFERENCE

1341
1342

Table 3.2. Alert levels during the fluoroscopy procedure and post-procedure trigger levels forpatient follow up (Stecker et al., 2009; NCRP, 2010; IAEA SAFRAD)
Dose parameter

Peak skin dose (PSD)

During the procedure
First notification Subsequent notificationlevel
level (increments)
2 Gy
0.5 GyPost-procedure
Trigger level for patient
follow-up
3–5 GyReference air kerma (Ka,r)

3 Gy

1 Gy

5 Gy

Cumulated air kerma area
product (PKA)

300 Gy cm2*

100 Gy cm2*

300 Gy·cm2 (cardiac andneuro interventions)
500 Gy·cm2 (others)

30 min15 min60 minutes

Fluoroscopy time

* Assuming a 100 cm2 field at the patient’s skin. The value should be adjusted to theactual procedural field size (Stecker et al., 2009).

1344

3.7. Practical advice for optimal performance of fluoroscopy procedures andpatient management

1345
1346
1347
1348
1349
1350
1351
1352
1353
1354

(129) Optimisation should consider radiation risk in conjunction with other non-radiation
related risks, e.g., use of contrast media, medications, sedation/anaesthesia, etc. The
optimisation task should not only include the current procedure, but should consider the patient
cumulative exposure, including potential future procedures that might be needed. This isespecially important for repeated FGI procedures to take account of cumulative skin dose fromprevious exposure increasing the risk of tissue reactions. Although repair of sublethal radiationskin injury is complete typically within one day; repopulation of cells can take several months.
Therefore the proper timing of a procedure and its optimal performance should be carefullybalanced for each individual patient and each clinical situation. The process includes actions
before, during and after the FGI procedure.

1355

3.7.1. Before the procedure

1356
1357
1358
1359
1360
1361
1362
1363
1364
1365
1366
1367
1368
1369
1370
1371
1372

(130) When a complex FGI procedure is proposed, patient medical and radiation history
should be reviewed, and the procedure appropriately planned. Previous diagnostic andtherapeutic procedures involving the use of ionising radiation should be reviewed. If necessary,
doses could be summed over a period of 60 days prior to the procedure for assessment of risk
(Fisher et al., 2021). Any relevant diagnostic images should be made available to the operator,
to reduce the need for additional diagnostic imaging before the procedure, and where imaging
is needed a preference given to ultrasound or MRI, to avoid unnecessary use of fluoroscopy
during the procedure.
(131) Guidelines should be prepared by the interventional team on methods for reducing thepotential for skin injuries such as use of different x-ray tube angulations to spread the skin dose,on the length of time left between repeat procedures (Angioplasty or other) relating to thepatient’s clinical condition, and on methods for identifying areas of previous exposure in order
to assist the minimisation of risk where appropriate.
(132) Departments performing FGI procedures should develop a standard checklist to identify
patients at higher risk and should have a written form to educate the patient and obtain writtenconsent before the procedure (ICRP, 2013a). An example of such a form is given in Box 3.6.
Three groups of patients require special attention in planning the procedure: paediatrics (see

1343

46

DRAFT REPORT FOR CONSULTATION: DO NOT REFERENCE

1373
1374
1375
1376
1377
1378
1379
1380
1381
1382
1383
1384
1385
1386
1387
1388
1389
1390

Section 5); pregnant patients (see Section 6); and patients at increased radiation risk for skin
injury due to genetics, or medications.
(133) Patients at increased risk for skin injury include obese patients (e.g., with body massindex greater than 30), those who underwent recent interventional or radiotherapy proceduresin the same body region, and those who might have higher sensitivity to radiation exposure.
When a repeated FGI procedure is planned, the prior medical history should be reviewed, thepatient’s skin should be examined, and the patient interviewed for previous or current skinreactions. All visible skin changes should be marked, so that their locations can be seen on the
fluoroscopic image. When there is a concern for radiosensitive skin, and the patient’s condition
allows, the planned FGI procedure should be performed at least 8–12 weeks after the previous
procedure in the same body area, and after at least 4–6 weeks when a different body area willbe irradiated (Balter et al., 2019).
(134) A standard policy for assessing pregnancy should be in place for facilities performing
FGI procedures to avoid accidental exposure of an embryo or fetus (see Section 6). If pregnancy
is established and the patient’s condition allows, the procedure should be deferred until after
delivery (ICRP, 2000a; ACR-SPR, 2018). This is especially the case for procedures in which
conceptus dose can exceed 10 mGy which include uterine embolisation, ovarian vein
embolisation, and endoscopic retrograde cholangiopancreatography (Dauer et al., 2012).
Box 3.6. Example of language for informed consent for radiation risks before ascheduled complex and potentially high dose interventional procedure (adapted from
Stecker et al. (2009))
You have been scheduled for an interventional [fluoroscopy-guided] procedure. This
involves the use of x-rays for imaging during the procedure and documenting the results.
Because of the nature of the planned procedure, it is possible that we will have to use
significant amounts of radiation. Potential radiation risks to you include:•

A slightly elevated risk of cancer later in life, not starting until several years after theprocedure. This risk is very low in comparison to the normal incidence of human cancer.
• Depending on the complexity of the procedure, a substantial amount of radiation may
occasionally need to be used. This could carry a risk of temporary skin injury or hair loss,
but any more severe radiation effect is very unlikely.
You (or your family) will be advised if substantial amounts of radiation were used during theprocedure. If this has occurred, you will be given written instructions requesting that a family
member checks the area of skin irradiated during the next 30 days for any redness or othersign of injury.
Sign and date here_______________ witness (physician)_______________date_____
1391

3.7.2. During the procedure1392

3.7.2.1. The team approach

1393
1394
1395
1396
1397
1398
1399

(135) Fluoroscopy is an interactive imaging procedure requiring proper use of equipment
features to perform the clinical task with the lowest possible radiation dose to the patient andstaff members. In addition to the main operator who has the primary responsibility for theprocedure outcome and for the patient and staff safety, other team members should have clearly
assigned functions to optimise the procedure time and the use of fluoroscopy and radiography.
These include patient comfort, cooperation and positioning; adjustment of the monitor display
and the console display; appropriate selection of catheters, wires, and devices; checks to ensure
47

DRAFT REPORT FOR CONSULTATION: DO NOT REFERENCE

1400
1401
1402
1403
1404
1405
1406
1407
1408
1409
1410
1411
1412
1413
1414
1415
1416
1417
1418
1419
1420
1421
1422
1423
1424
1425
1426
1427
1428
1429
1430
1431
1432
1433
1434
1435
1436
1437
1438

everyone is wearing a radiation dosemeter; and considering the use of alternative image
guidance such as ultrasound.
(136) Good practice is for the fluoroscopy team to include a dedicated radiographer to operate
the equipment controls, especially when complex FGI procedures are performed, although thiswill be done by radiologists or cardiologists in some countries. In cases when the controls areoperated by physicians performing the procedure, they should be capable of performing this asa multi-task function. They will need to simultaneously manipulate a catheter or administer
contrast, evaluate the image on the display, monitor the patient’s condition, and at the sametime select proper fluoroscopy position and projection, select the proper programme from theconsole, operate the beam, and use the minimum amount of fluoroscopy and number ofradiographic images.
(137) Other team members should also play a part in optimisation of a procedure, e.g., a nurse
or radiographer can be responsible for proper positioning of the radiological protection screens,
another team member should monitor dose factors and notify the operator when pre-definedlevels are reached. Regardless of who operates equipment, the roles should be pre-defined,
functions optimised and the team well trained. A pre-procedure ‘time out’ in which teammembers run through a checklist should be considered. No person should be present in theroom without a clear role. Team cooperation and awareness of radiation safety culture are
crucial for the success of an FGI procedure. An example of a checklist including all decisions
about a procedure can be reviewed at (Image Gently, 2022b).
(138) Every team member should have sufficient knowledge on how to reduce their own
radiation exposure by proper positioning in the room and using the three basic principles ofprotection: time, distance and shielding. Radiological protection shields and individual
protective equipment should be properly selected and properly used, as recommended in
Publication 139 (ICRP, 2018b).
(139) A successful procedure is reliant upon patient cooperation. Patients should be briefed
prior to the commencement of the procedure so that they know what to expect and how tocooperate. Less cooperative patients, e.g., young children, might need to be sedated if patient
immobilisation cannot be achieved by other means. More information can be found in Section
5. The decision should be taken by balancing the risk of sedation and the risk of compromised
image quality and procedure outcome.
(140) Potential doses to staff performing interventional procedures from radiation scatteredfrom the patient are also a concern, particularly from long complex interventional procedures.
Aspects relating to occupational protection during such procedures are considered in
Publication 139 (ICRP, 2018b). Occupational exposure in interventional procedures is closely
related to patient exposure and, therefore, management of occupational protection should be
integrated with patient protection. Staff needs to apply the basic radiation protection principles
and make effective use of protective devices. Measures to protect staff should not impair theclinical outcome, and should not increase patient exposure.

1439

3.7.2.2. Operator selection of x-ray tube and image receptor position and exposure modes

1440
1441
1442
1443
1444
1445
1446

(141) Factors related to the geometric configuration and exposure mode are selectable by theoperator and influence image quality and patient and staff radiation exposure. Those related to
exposure mode have been discussed in Section 3.2.2(142) Geometric factors include positioning of the x-ray system in relation to the anatomical
region, projection, table height, and focus-to-image receptor distance. In C-arm systems, it ispreferable from a radiological protection perspective to keep the x-ray tube under the patient
table. The distance between the x-ray tube and patient should always be maximised to reduce48

DRAFT REPORT FOR CONSULTATION: DO NOT REFERENCE

1447
1448
1449
1450
1451
1452

patient dose. In C-arms with the x-ray tube fixed in relation to the isocentre, the patient couchshould be kept as high as practicable for the operator to manipulate. In isocentric techniques,e.g., for cardiac interventions, the table height should be selected such that the object of interest
is in or close to the C-arm isocentre to allow for best image quality. The image receptor should
be positioned as close to the patient as possible; this reduces patient and staff exposure fromscatter radiation and reduces the geometric blurring.

1453

3.7.2.3. X-ray beam projection and collimation

1454
1455
1456
1457
1458
1459
1460
1461
1462
1463
1464
1465
1466
1467
1468
1469

(143) X-ray beam projection and angulation should be selected to provide the required
anatomical visualisation but considering also that staff dose rate is higher at oblique or
horizontal projections in which the x-ray tube is on the operator side. Patients’ extremities
should be kept out of the beam to avoid higher dose rates selected by the ADRS when object
thickness is increased. The use of steep angulations increases patient dose, passing throughthicker more lateral sections of the body, should be minimised when possible. Typically, each
3 cm thickness of additional tissue doubles the dose rate to the patient. For long procedures thearea of skin where the x-ray beam is incident upon the patient should be changed during theprocedure by modifying the C-arm angulation, to reduce peak skin dose and avoid skin injury.
(144) Proper collimation of the primary x-ray beam will reduce the irradiated volume in thepatient and the amount of scattered radiation, which improves the image contrast. This will also
reduce a possible overlap of the radiation fields from different projections, thus helping tokeeping the peak skin dose below the threshold for skin injury. Patient and staff dose can be
reduced with no loss of image quality by using automatic positioning systems or virtual
collimation when available. Image contrast can be improved by properly positioning wedge
filters and other functions of the fluoroscopy system, when available.

1470

3.7.2.4. Protocol selection and adjustment

1471
1472
1473
1474
1475
1476
1477
1478
1479
1480
1481
1482
1483
1484
1485
1486
1487
1488
1489
1490
1491

(145) Optimisation of the clinical procedure requires selection of the best available protocol,
tailored to the patient characteristics, to achieve the clinical goal. Communication before andduring the procedure is critical. The physician and radiographer will often need to adjust theexamination protocol for both the patient needs (patient size, potential motion concerns, etc)
and the clinical issues (safety, contrast limits, magnification of small body parts, etc).
(146) The anti-scatter grid should be removed for procedures that result in low levels of
scattered radiation, e.g., those involving small children or where body thicknesses is less than
10 cm.
(147) High dose rate modes in fluoroscopy should be used only when indispensable and forthe minimum time necessary for the procedure. The lowest dose rate mode should be set as adefault, and to require the operator to manually select the higher dose rate mode only whenhigher image quality is needed. For example, lower image quality can be tolerated when
fluoroscopy is used to navigate insertion of a catheter or tube, and higher image quality isneeded for viewing small vessels after contrast administration.
(148) The operator has full control over activating the fluoroscopy or radiography acquisition
modes and should minimise fluoroscopy time and use the minimum number of acquired images
consistent with the procedure. Whenever possible, the LIH and LSH function should be usedand storing of the last fluoroscopy loop instead of acquiring radiography or cine images.
(149) Box 3.7 provides summary practical advice on optimisation (ICRP, 2013a). This should
be included in initial and periodic radiological protection training of medical staff, andpreferably provided in written form.
49

DRAFT REPORT FOR CONSULTATION: DO NOT REFERENCE

Box 3.7. Practical techniques to reduce patient dose.
Fluoroscopy dose
• Use a low-dose-rate fluoroscopy mode when possible• Use a low-pulse-rate fluoroscopy mode when possible• Remove the grid when performing procedures on small children and thin adults (<10 cm
abdominal thickness)• Use the lowest-dose mode for image (cine) acquisition that is compatible with the required
image quality• Minimise fluoroscopy time – consider ultrasound to guide devices and observe motion• Use the last-image-hold function for image store and review, when possible, instead ofimage exposure or using fluoroscopy• When possible, use ‘last series hold’, also referred to as ‘video loop’, if available insteadof performing a cine run• If available, use a stored fluoroscopy loop for review instead of using fluoroscopy
Cine dose and DSA• Minimise the number of cine series• Minimise the number of frames per cine series• Never use cine as a substitute for fluoroscopy• Sometimes cine runs can be replaced by last screen hold
Other factors• Collimate the radiation beam to the area of interest• Use accurate collimation for protection of the gonads, rather than gonad shields• Use virtual collimation if it is available• Use wedge filters when they are appropriate• Keep the image detector (image intensifier or flat panel) as close as possible to the patient• Keep the patient as far as possible from the x-ray tube
• Try to avoid steeply angulated projections (especially left anterior oblique cranial)• Try to vary the C-arm angulation slightly to avoid concentrating the radiation dose at asingle site on the patient’s skin
• Use magnification only when necessary• Remember that for large patients, and also for steeply angulated projections, the dose to
the patient increases substantially
Monitoring dose
• Pay attention to the patient radiation dose display in the procedure room
• If the patient has had previous similar procedures, try to obtain information about theprevious radiation doses to optimise subsequent procedures• Track cumulative dose and set dose alerts if cumulative dose exceeds certain levels (suchas 3 Gy peak skin dose (PSD) or 5 Gy cumulative air kerma (Ka,r)
1492
1493
1494
1495

(150) If conventional image intensifiers are used, the use of electronic magnification should
be limited to cases when high spatial resolution is needed, which cannot be achieved with thenon-magnified image. Whenever available, digital magnification should be used instead of50

DRAFT REPORT FOR CONSULTATION: DO NOT REFERENCE

1496
1497
1498
1499
1500
1501
1502
1503

electronic magnification.
(151) Operators should avoid placing their hands or objects such as contrast syringes in the
primary beam, as this will increase the dose rate to the patient and the scattered dose rate.
(152) In some minimally invasive vascular and non-vascular interventions such as inperipheral insertion of central catheter (PICC) placement, endourology or gastroenterology,
patient and staff dose can be reduced by using ultrasound images to guide device placement,
thus limiting the use of fluoroscopy to only moments when better image quality is needed to
localise the object of interest or monitor the procedure development.

1504

3.7.3. After the procedure

1505
1506
1507
1508
1509
1510
1511
1512
1513
1514
1515
1516
1517
1518
1519
1520
1521
1522
1523
1524
1525

(153) Patient radiation dose reports should be produced at the end of the procedure andarchived in the departmental records and patient medical record. The information should be
used for performing periodic dose audits and benchmarking the practice against available
DRLs and to indicate when optimisation is needed. Specialised dose monitoring softwaresystems storing dose information in a database can enable more powerful analyses to be
performed (Fernandez-Soto et al., 2015; ICRP, 2017; Vano et al., 2022).
(154) Departments should establish a programme for follow-up of patients when any of the
pre-defined trigger values described in Section 3.6 is exceeded. It is likely that some skin
injuries are missed or mis-diagnosed because of lack of follow-up. The operator should write
an appropriate note in the patient’s medical record, stating that a substantial radiation dose has
been administered, and indicating the reason. In this case, clinical follow-up is essential forearly detection and management of potential skin injuries (NCRP, 2010; ICRP, 2013a). A
standard form would be useful to record the information, possibly with an anatomical sketch
on which areas that might have received a high skin dose could be marked.
(155) The patient or their carer should be advised of the possibility of a skin injury due to atissue reaction and should be told to examine the beam entrance site 2–4 weeks after theprocedure and to notify the operator if any skin changes are seen. Examples of post-procedure
patient discharge instructions for high dose procedures is given in Box 3.8. Patients who havenot previously notified the operator should be contacted by telephone approximately 30 days
after the procedure in order to ensure that a skin injury is not missed (ICRP, 2013a).
Box 3.8 Example of post-procedure patient discharge instructions for high doseinterventional procedures (adapted from Stecker et al. (2009))
X-Ray usage - one of these two boxes is checked as part of the discharge instruction process:• Your procedure was completed without the use of substantial amounts of x-rays. No
special follow-up is needed because radiation side effects are highly unlikely.
•

1526
1527
1528
1529
1530
1531

Your procedure required the use of substantial amounts of x-rays. Radiation side-effects
are unlikely but possible. Please have a family member or carer inspect your(back/neck/scalp/…..) 30 days from today, for signs of skin redness or rash .
Please call ####### and tell us whether or not anything is seen.

(156) If a skin injury is suspected, the interventionalist should see the patient at an office visit
and should arrange for appropriate follow-up care. The physician responsible for the patient’s
care should be informed of the possibility of radiation effects (Stecker et al., 2009; NCRP, 2010;
IAEA SAFRAD). In addition, it is recommended that sites where interventional procedures are
performed should establish a team that includes a physician, medical physicist andradiographers to review protocols in cases when the patient skin dose exceeds certain51

DRAFT REPORT FOR CONSULTATION: DO NOT REFERENCE

1532

preselected levels.

1533

3.8. Dose management QA programme

1534
1535
1536
1537
1538
1539
1540
1541

(157) As outlined throughout this chapter the development of a successful Dose Management
QA programme is an essential part of radiological protection and optimisation (see Section 3.7).
Components of the QA programme dealing with dose management should be put in place toenable the optimisation process to progress and a core team established to promote optimisation
through reviews of common fluoroscopic procedures. In addition to the equipment selection,
facility design, maintenance and QC tests discussed in Section 2 of Publication 15X, forfluoroscopy guided procedures, QA should include additional attention to the following
components (ICRP, 2013a, 2018b, 2022):

1542
1543
1544
1545
1546
1547
1548
1549
1550
1551
1552
1553
1554
1555
1556

•
•
•
•
•
•
•
•

Availability of radiological protection tools, dosimeters and their use.
Availability of adequate personnel and their responsibilities.
Training in radiological protection (initial and continuing).
Patient and staff dose monitoring and dose audit.
Clinical follow-up for high patient radiation doses.
Image quality and procedure evaluation.
Reporting and QA for unintended or accidental exposures.
Training in radiological protection (RP) ethics, teamwork, safety culture,communication(158) The complexity of the Dose Management QA programme and the level of performanceand optimisation will depend on the arrangements that are in place for each of the aspects
described in ICRP (2022): professional skills and collaboration; methodology and technology,
and organisational processes and documentation. Box 3.9 presents the arrangements that should
be in place for fluoroscopy facilities at different levels of development: C (basic), B(intermediate) and A (advanced).

52

DRAFT REPORT FOR CONSULTATION: DO NOT REFERENCE

Box. 3.9. Arrangements that should be in place for fluoroscopy facilities at different
levels of development and complexity
C: Basic
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•

Requests for fluoroscopy procedure include reason for referral and some clinical historyof patient.
Operators knowledgeable on equipment features, programmes and modes.
Operators and all personnel involved trained to perform procedure with minimum amountof radiation for patient and staff
Radiological protection personal protective equipment available and properly used.
Selectable pre-defined study protocols and acquisition programmes for common clinicalconditions available and optimised for the clinical tasks performed with the equipment.
Pulsed fluoroscopy, pulsed image acquisition modes, beam shaping filters and “wedge”
filters in use.
Different ADRC programmes available for different anatomic regions.
ADRC settings for different modes and anatomical/clinical programmes tested, adjusted
and baseline values of IAK rates at the image receptor set at commissioning.
Lowest dose rate fluoroscopy mode set as default.
DSA function available for FGI vascular procedures.
Regulatory limit for the maximum patient ESAK rate met at commissioning.
Last image hold function available and used.
QC tests to characterise system performance carried out at least annually by a qualified
medical physicist.
Regular constancy checks performed by a local qualified staff, e.g., physicist /radiographer / x-ray engineer
Dose display available and report of cumulated values for FGIs.
Verification of calibration of dose displays performed as a part of QC.
Local audits of patient dose quantities for a common protocol performed by a trained staff
member.
Cumulated patient dose values recorded after the procedure in the departmental records
and patient medical records.
Follow-up programme established for patients at risk of tissue reaction set if dose values
exceed pre-defined trigger levels.

B: Intermediate• Requests for fluoroscopy procedures include reason for referral and with clinical historyof patient, including pre-procedure diagnostic imaging and information on all previous
FGI procedures available in the Electronic Medical Record (EMR).
• Use of pre-procedure checklist for procedure optimisation by core clinical team
• Standard review process exists to identify patients at higher risk, obtain written consent
before FGI procedures, and plan procedure properly.
1557
53

DRAFT REPORT FOR CONSULTATION: DO NOT REFERENCE

1558

Box. 3.9. (Continued)
B: Intermediate (continued)
•
•
•
•
•
•
•
•
•
•
•

•
•
•

Protocols for common clinical referrals used for the same clinical indications throughout
facility agreed.
Clear procedures set for selecting the most appropriate fluoroscopy system available in theorganisation for answering a full range of clinical questions.
ADRC based on fully automatic adjustment of exposure parameters
Dose display available and report of cumulated values exportable in a standard format for
all fluoroscopy procedures.
Features such as “spot fluoroscopy”, automatic positioning systems, “virtual collimator”
and "live zoom" are available and used.
Store and replay function available and used.
Large extra bright image monitors utilised for FGI procedures.
CBCT utilised and optimised for FGI procedures.
Road mapping used for FGI vascular procedures.
Optimal system performance set in collaboration between vendor representatives and local
core team.
Comprehensive QC programme established for testing equipment performance in terms ofimage quality and dose parameters using standard phantoms and test objects, representing
a range of patient sizes.
The scope and content of the QC programme, the limiting values and the frequency of
testing at appropriate levels for the intended clinical use of the equipment.
Information about peak skin dose and/or skin dose mapping available in real time during
the FGI procedure and recorded after the procedure.
Alert levels set and procedure established to monitor dose values throughout the procedureand notify the operator.

A: Advanced
•
•

•
•
•
•

Consistent nomenclature and naming of clinical imaging protocols throughout
organisation, across multiple facilities and equipment.
Harmonised performance settings for all fluoroscopy systems of similar type anduniformity of performance between different systems in multi-facility, multi-siteorganisations, and multiple physician groups.
Process of core team continual review and assessment of protocols in place.
Near miss and error tracking with systems improvement processes.
Application of dose monitoring software to store dose data and analyse performance.
Task-based model observer evaluations of system imaging performance established.
Comprehensive system for patient follow-up with training of all healthcare practitioners
involved in different stages of the patient clinical pathway.

54

DRAFT REPORT FOR CONSULTATION: DO NOT REFERENCE

1559

4. MULTI-DETECTOR COMPUTED TOMOGRAPHY

1560
1561
1562
1563

(159) Key messages in this section:• Protocol optimisation can result in significant dose reduction but depends on
appropriate selection of scanning parameters and an understanding of theinterdependence of the exposure parameters.

1564
1565

•

Lower noise levels are required for imaging thinner patients because of the absenceof adipose tissue between organs, particularly when viewing low contrast anatomy.

1566
1567
1568
1569
1570

•

Thinner CT slices enable versatile volumetric 3D image representations and can
improve contrast resolution between small structures and the background when theslice thickness is similar to the dimension of the structure, but the noise level will behigher which is acceptable if the final reviewed image data has sufficient image
quality.

1571
1572
1573

•

Tube-voltage reduction may enable radiation dose reduction by improving the CNR
for iodine contrast studies, but typically involve a compensatory increase in tube
current to reduce the noise level to achieve acceptable clinical image quality.

1574
1575
1576

•

Iterative reconstruction (IR) and deep-learning based image reconstruction (DLIR)
have the potential to produce better image quality and mitigate image artefacts, sothat protocols may use lower dose settings to obtain adequate clinical image quality.

1577
1578
1579
1580

•

Automatic tube current modulation (ATCM) accounts for differences in patient size
and tissue attenuation. It adjusts the mA to maintain a similar level of image quality
throughout a scan, however, CT operators need to understand concepts on whichmA adjustments are based and that image quality references vary between vendors.

1581
1582
1583

•

For cardiac imaging CT scanners can be set up to trigger scans at pre-selected phasesof the cardiac cycle determined from the ECG and this can provide good image
quality at relatively low doses with low and stable heart rates.

1584
1585
1586
1587

•

Protocols should be set up initially for examinations that are performed frequently
and ones that are for urgent indications. The level of image quality, exposure factors,
slice thickness, pitch, filters, and the need for iterative or deep-learning based
reconstruction should be agreed among the professionals involved.

1588
1589
1590
1591

•

Scan protocols should be reviewed periodically and protocol development be acontinuing process with measurements being made of the impact of changes. New
protocols should be tested against old ones, and practical assessments made on
phantoms if required.

1592

4.1. The increasing use of computed tomography

1593
1594
1595
1596
1597
1598
1599
1600

(160) Since the first clinical images in 1971, computed tomography (CT) scanning has
increased steadily in importance as the sophistication, speed, and flexibility of equipment andsoftware have evolved. Reconstructed CT images show cross sections through the body, so
unlike other forms of imaging, the images of overlying tissues are not superimposed. As a result,
CT has reduced or eliminated exploratory surgeries and there is a greater potential for
identification of abnormal pathology and changes in tissue structure. However, these additional
capabilities are usually related to increased radiation exposure. Studies of radiation doses topatients from around the world indicate that where CT scanners are in use, 50%-70% of the55

DRAFT REPORT FOR CONSULTATION: DO NOT REFERENCE

1601
1602
1603
1604
1605
1606
1607
1608
1609
1610
1611
1612
1613
1614
1615
1616
1617
1618
1619
1620
1621
1622
1623
1624
1625
1626
1627
1628
1629
1630
1631
1632
1633
1634
1635
1636
1637
1638
1639
1640
1641
1642
1643
1644
1645
1646
1647
1648
1649

dose from medical imaging procedures arises from the CT component (Mettler et al., 2008;
Hart et al., 2010; NCRP, 2019). Moreover, the number of CT scans continues to increase inmany countries with the demand for additional clinical information provided by 3D volumetricimage data and post-processing (Dovales et al., 2016; Bly et al., 2020). Wide variations in doses
are observed in large dose surveys even among facilities using similar CT scanner models andfor similar scan indications (Mettler et al., 2008; Martin and Huda, 2013; Shrimpton et al.,2014; Epko et al., 2018; Smith-Bindman et al., 2019). Dose levels continue to be reduced bothby vendor equipment and software improvements and by educational programmes in many
countries as a result of raised awareness about the need for optimisation (IAEA/WHO, 2012).
However, a wide variability in CT doses still exists among countries and continents for similar
clinical indications (Smith-Bindman et al., 2019). These differences are related to available CT
technology, personnel training on dose optimisation and patient workflow, and the lack of anadequate dose management as part of the QA programme for CT system resources. There is
still much to be achieved in terms of optimisation of protection worldwide, which requiresconsideration of the existing resources and challenges in each region (Kanal et al., 2017;
Matsunaga et al., 2019; Vassileva et al., 2015).
(161) As with other imaging equipment, when a new CT facility is set up or an older system
replaced, selection of the appropriate scanner should be carried out by a multi-disciplinary teamof radiological professionals (ICRP, 2022). The number of slices ranges from 16 upwards andthe beam coverage in terms of the length of anatomy imaged in a single axial rotation can varyby a factor of 4-5. Other factors that affect performance are the sensitivity of the detectors andthe reconstruction method, which will have a decisive effect on clinical image quality and thus
indirectly on the required level of dose (Vassileva et al., 2015). Apart from specifications for
the CT scanner itself, ancillary equipment such as workstations, software or other clinicalapplication platforms should be powerful enough to handle the large numbers of images
generated and there should be a maintenance contract in place sufficient to ensure continual
operation. Specification, site-planning and purchase of CT equipment all require carefulconsideration of the cost and benefit (Mahesh and Hevezi, 2010).
(162) The next step is protocol optimisation, potential dose reduction, with CT depends on
appropriate selection of scanning parameters (both acquisition and reconstruction). Significant
dose reduction is sometimes possible, but it is necessary to understand the interdependence ofthe various parameters in order to achieve this. Sufficient support and training for users fromapplications specialists and medical physicists are essential to ensure that advantage is takenof all the CT capabilities provided. Multiple dose reduction features are incorporated into new
CT scanner models, but unnecessarily high doses can be delivered if parameters are set
incorrectly and/or multiple passes through a body part are performed unnecessarily. The
quantities used to record patient dose that are displayed on scanner consoles are the volume CT
dose index (CTDIvol) and dose length product (DLP) (Box 4.1). Tissue reactions in the formof skin injury and hair loss are rare, but have been reported during CT perfusion measurements
either combined with digital subtraction angiography (Imanishi et al., 2005) or from poor
understanding of tube current modulation functionality (ICRP, 2007a; Martin et al., 2017).
(163) All CT scanners must be covered by a comprehensive programme of QC tests, startingfrom the acceptance and commissioning phase with a new scanner and including
comprehensive regular tests by medical physicists and daily basic QC by radiographers (ICRP,
2022; ACR, 2022). The impact that exposure parameters have on patient dose or potential
issues on the system performance hindering diagnostic image quality, will go undetected,
unless scanner performance is characterised and dose levels and image quality are monitored.
The scientific skills of the physicist in measuring, analysing and interpreting these test results
combined with the clinical experience of the radiologist and radiographer are crucial in this56

DRAFT REPORT FOR CONSULTATION: DO NOT REFERENCE

1650
1651

process. The information gained will play a major role in optimisation of radiologicalprotection and keeping CT doses at an acceptable level (ICRP, 2000c, 2007a).
Box 4.1. CT dosimetry quantities (ICRU terminology given in Annex A)
The CT dose index (CTDI) and dose length product (DLP) are the quantities used forevaluation of CT scanner doses.
CTDI: The CTDI is the integral of the CT axial air kerma profile along the z axis of rotationof the CT scanner for a single rotation, divided by the nominal width of the beam (IAEA,
2007). By convention the CTDI is measured with an ionisation chamber, 100 cm in length.
Scanner output: The CTDI measured free in air provides a record related to scanner output.
CTDIvol: The CTDI measured in standard polymethylmethacrylate (PMMA) cylindricalphantoms representing the head (16 cm diameter) and body (32 cm diameter) provides
measurements that relate to the doses to patient tissues. Measurements made at the centre
CTDIc and periphery CTDIp of the phantoms are weighted 1:2 to obtain an average weighted
CTDI. An adjustment for the pitch of helical scans is made to derive a volume averaged
CTDI (CTDIvol) that is displayed on scanner consoles (Section 4.2.4).
DLP: The CTDIvol can be multiplied by scan length to derive the DLP that relates to the dosefrom a complete CT scan, which is also displayed on CT scanner consoles.
Size-specific dose estimate (SSDE): CTDIvol assessments are based on standard phantoms
and take no account of differences in patient size which varies greatly, especially in thepaediatric age range. Correction factors can be used to derive SSDE values based on thedimensions of individual patients (AAPM, 2011a, 2014, 2019a) and it is planned that thesewill also be displayed on scanner consoles in the future.

1652

4.2. The CT image1653

4.2.1. CT numbers, noise, slice thickness and contrast

1654
1655
1656
1657
1658
1659
1660
1661
1662
1663
1664
1665
1666

(164) As with all other x-ray imaging techniques, CT image contrast is determined based on
x-ray attenuation of the target material or tissue. However, the CT contrast scale is calibrated
based on the attenuation of water. More specifically, CT contrast is defined in terms of CT
number in Hounsfield units (HU), describing the linear attenuation of x-rays in the target
relative to the linear attenuation of x-rays in water. Water is set at zero (0 HU) and air withpractically zero attenuation at −1000 HU.
(165) The diagnostic value of CT images does not change appreciably when the dose level isincreased above the required level for a specific clinical indication (aside from potential
incidental findings) (Fig.4.1). Therefore, a proper definition of required clinical image quality
is needed for optimised CT imaging. Basic objective measures of image quality such as image
noise and contrast to noise ratio (CNR) are relatively easy to perform, but do not capture all of
the features relevant to making a correct clinical diagnosis. An approach might be to require
specific noise levels for designated diagnostic tasks.

57

DRAFT REPORT FOR CONSULTATION: DO NOT REFERENCE

1667
1668
1669
1670
1671
1672

Fig. 4.1. CT chest images with contrast taken at 120 kV. The image on the left is with thestandard exposure and the one on the right has double the mAs. The clinical image quality
difference between the two images is slight and there is no gain in diagnostic information fromthe higher exposure. CT exposure factors are strongly dependent on patient size. (K. Applegate,
Dept of Radiology, University of Kentucky, retired)

1673
1674
1675
1676
1677
1678
1679
1680
1681
1682
1683
1684
1685
1686
1687
1688
1689
1690
1691
1692
1693
1694
1695
1696
1697
1698
1699
1700

(166) However, ‘optimal’ image quality involves a combination of quantitative metrics
including noise, observer perceptions, and training and experience of the interpreter, anddepends on the task and type of patient. For instance, imaging of paediatric or thin adult patients
may require a lower noise level compared to larger patients because of the absence of adipose
tissue between organs and tissue planes and the smaller anatomical dimensions, particularly
when viewing low contrast anatomy (Wilting et al., 2001; McCollough et al., 2002; Boone etal., 2003), but low dose options with higher noise are sufficient in some circumstances (see Fig.
5.3 in Section 5.2.4).
(167) As a rough estimate of the dose reduction potential in paediatric body CT scans, themAs can be reduced by a factor of 4 to 5 from adult techniques to infants, while for obese
patients, it might be increased by a factor of two (McCollough et al., 2002). This will be
discussed in a later section when automatic tube current modulation is considered.
(168) If the thickness of the reconstructed image is reduced, a higher mAs will be required toprovide the equivalent signal to noise ratio (SNR) within the width of the thinner slice. In
modern CT scanning, image data are often acquired with thin slices that have roughly the samevoxel dimension in the x, y and z directions (i.e. isotropic resolution). This enables subsequentmultiplanar reformats (MPR), modality image co-registration, annotation, and/or 3D review tobe performed by radiologists. These thin source image reconstructions will have higher image
noise levels than are seen in the final reformats with thicker slices or 3D visualisations. For agiven mAs, the use of thinner slices increases image noise, but can improve the contrast
resolution between small features and the background when the slice thickness is similar to thedimensions of the features, by reducing the contrast averaging that results from the ‘partial
volume effect’.
(169) CT contrast media typically involve iodine-based compounds (ACR, 2021). The
injected intravenous (IV) contrast media will increase attenuation of arteries and/or veins in
CT angiography scans and highly perfused tissues in contrast enhanced CT scans, aiding theidentification of lesions. Contrast media are also used to study tissue function, throughrecording images before and after administration of the contrast medium (pre-contrast and post58

DRAFT REPORT FOR CONSULTATION: DO NOT REFERENCE

1701
1702
1703
1704
1705
1706
1707
1708
1709
1710
1711

contrast), or as a dynamic scan, e.g., in perfusion studies with a sequentially acquired series ofimages. Strict timing of imaging is required with respect to the passage of contrast in order toachieve a satisfactory result when the contrast enhancement is at its peak for the specific organand patient’s physiological status. This is particularly important for paediatric patients(Mortensen and Tann, 2018) and when imaging targets with rapid biokinetics (e.g., cardiac or
coronary CT angiography). The higher contrast properties of iodine allow lower tube potential(and lower radiation dose) protocols in CT angiography (CTA) to be an effective method of
optimisation. CTA examinations are usually short or ultrashort, so the volume of injected
contrast is lower than in conventional CT. Contrast media can be administered safely at room
temperature without increased risk of extravasation; although both allergic reactions and renal
contrast nephropathy carry real but very low risks (ACR, 2021).

1712

4.2.2. Scan projection radiograph and scan range

1713
1714
1715
1716
1717
1718
1719
1720
1721
1722
1723
1724
1725
1726
1727
1728
1729
1730
1731
1732
1733
1734
1735
1736
1737
1738
1739
1740
1741
1742
1743
1744
1745
1746
1747

(170) In order to select the range for a CT scan, a low dose scan projection radiograph (SPR)
is recorded with the x-ray tube held in a fixed angular position while the patient is transported
through the gantry (z-axis). A variety of terms are used for the SPR by different vendors:
namely scout view, topogram, surview, or scanogram, and the projection chosen can be
antero-posterior (AP), postero-anterior (PA) and/or lateral. Furthermore, a single or double SPR
may be required to set up the scan. The range of the scan in the longitudinal (z) direction, theaxial field of view and optional scan tilt angle (for most equipment) can then be selected on the
SPR image and the patient positioned automatically to scan the selected regions. The preference
on the SPR direction and number of SPRs needed before the actual CT scan varies according
to the vendor, scanner model and even scanner software version. It is important to be aware of
the SPR recommendation because SPR has a direct effect on the automatic tube current
modulation (ATCM) and automatic tube voltage selection (ATVS) performance, and as a resulton patient dose and image quality.
(171) During routine scans of the brain, the gantry may be tilted to reduce the radiation doseto the eyes and for this a lateral SPR is used (Yeoman et al., 1992; Heaney and Norvill, 2006;
Nikupaavo et al., 2015). In the absence of organ dose modulation (see Section 4.4.4) and theability to tilt the gantry, the protection of eye lenses in head CT scans can also be implemented
by tilting the patient head forward by using a support cushion of light-foam radiotransparent
material placed under the occipital part during the scan (Van Straten et al., 2007). This method
necessitates that the patient being able to tilt their head accordingly, which may not be an option
with trauma or mobility compromised patients. Modern CTs may also offer organ dose
modulation to reduce dose to the eyes. The use of shielding on the eyes is discouraged due tosuboptimal effects on image quality, the overall image acquisition, and patient acceptance.
(172) During a helical CT scan, additional data and consequently small amounts of additionalrotational irradiation are required at the beginning and end of the scan range for image
reconstruction. The additional exposure, referred to as overranging, increases with pitch size
and with applied beam collimation (Section 4.2.4). Modern CT scanners are equipped withdynamic collimation using moving beam shutters that will attenuate parts of the x-ray beam at
the beginning and end of helical scans to limit the additional exposure. The potential amountof overranging is more relevant in dose optimisation when the exposed organ outside theplanned region is radiosensitive (for example the thyroid in head scans of paediatric patientsor younger adults) and can be estimated using Gafchromic film.
(173) The radiation exposure to a patient is mainly dependent on the applied dose level(estimated through the CTDIvol and size corrected as SSDE) and the anatomical length of the
exposure to the body, including repeat passes through it (measured by the DLP, Box 4.1).
59

DRAFT REPORT FOR CONSULTATION: DO NOT REFERENCE

1748
1749
1750
1751
1752
1753
1754
1755
1756
1757
1758

Therefore, the scan range should be limited to the region of interest within the body in order toavoid unnecessary radiation dose to organs outside the target range. The boundary definition
based on the individual scan indication is particularly important for paediatric patients, who
are in general more radiosensitive and in whom organs are in closer proximity.
(174) When using ultra-low dose imaging protocols in CT, the radiation exposure from the
SPR may be of the same order of magnitude as the helical scan (Schmidt et al., 2013). Thisemphasises the need to optimise the whole CT examination including the SPR. Optimisation
may involve use of a single SPR instead of two SPRs (AP/PA and lateral) or applying a lower
mA. However, vendor recommendations should be followed to ensure that the image signal isadequate for proper ATCM and ATVS functionality (Section 4.4). In certain scanner models, it
is possible to apply additional tin filtration to reduce the SPR radiation dose significantly.

1759

4.2.3. Tube potential and filtration

1760
1761
1762
1763
1764
1765
1766
1767
1768
1769
1770
1771
1772
1773
1774

(175) CT scanners use a heavily filtered beam (many millimetres of aluminium equivalent)
and tube potentials between 70 and 150 kV can been applied, depending on the patient size,
morphology, intended clinical task and whether iodinated contrast is used.
(176) High tube potentials are required for scanning highly attenuating regions in larger
patients to avoid photon starvation, but lower tube potentials provide better contrast forincreased iodine concentrations and for smaller patients (Rampado et al., 2009). Values of 100
kV or 80 kV increase the CNR for iodinated contrast in vascular tissues by 25% or 65%
respectively (Itatani et al., 2013; Taguchi et al., 2018). Low-kV protocols have significant
potential for radiation dose reduction and improving image quality in CT angiography (Talei
Franzesi et al., 2018) and detection of vascularised liver tumours (Lee et al., 2012b). This is achallenge with larger patients and less-powerful CT scanners because of the more limited xray penetration (Aschoff et al., 2017). However, some modern CT scanners can overcome thislimitation by offering tube currents up to 1300 mA with lower kilovoltages (Lell andKachelriess, 2020). Guidance on manual selection of kV settings for patients of varying size isgiven in Box 4.2.
Box 4.2. Choosing the tube potential for a CT scan
The optimum tube potential depends on body size and use of low tube potentials is moreadvantageous for examinations using iodine contrast. Recommended tube potentials are
given here in terms of the sum of AP and lateral body dimensions in cm (Ranallo, 2013;
AAPM, 2022).
Head scanskV

Body scans, dimensionkV

Paediatric 0–2 y

70–80

Paediatric; < 44 cm

70–80

Paediatric 2–6 y with contrast

80–100

Paediatric and adult; 44–60 cm

100

Paediatric 2–6 y no contrast

100–110Adult with contrast

100–120

Medium and large adults; 60–80 cm

120

Adult CT perfusion

80–90

Extra large adults: 80 cm

140

Adult no contrast

100–120Adult upper thorax through shoulders

120

N.B. These values provide guidance, but will not be universally appropriate, because of differencesin CT scanner models. The inherent filtration varies with the CT scanner, so the x-ray spectra will
also vary. Moreover, some new scanners have the capability to generate tube currents over 1000 mA
with lower kilovoltages, enabling their use with larger patients, when appropriate.

60

DRAFT REPORT FOR CONSULTATION: DO NOT REFERENCE

1775
1776
1777
1778
1779
1780
1781
1782
1783
1784
1785
1786
1787
1788
1789
1790
1791
1792
1793
1794
1795
1796
1797
1798
1799
1800
1801
1802
1803
1804

(177) A lower tube potential will significantly decrease patient dose if the same tube current(mA) is maintained, but the noise level will rise as the x-rays are attenuated more heavily, so it
may be necessary to increase the mA to some extent to recover image quality in terms of noise.
The iodine can be used as a metric to monitor image quality and assess the appropriate increase
in mA as kV is reduced, for structures enhanced with contrast media. The image quality
advantages of low tube potential are limited for soft tissue structures with little or no contrast
enhancement. Thus, the image quality without contrast enhancement is related almost entirely
to noise level. Image quality in terms of low contrast visualisation and noise level, and patient
dose should be monitored when making a change for non-contrast procedures.
(178) Tube potential can be selected manually depending on size for each patient in a similarmanner to radiography examinations. However, most companies now offer the option to use
information from the SPR to optimise tube potential automatically as well as mA (Winklehneret al., 2011). Clinical studies have demonstrated that scanning with automatic tube voltage
selection (ATVS) can provide images with improved contrast at reduced patient doses (Mayer
et al., 2014).
(179) Patients are round (infants and young children) or oval (adults) in cross section andwhen they are irradiated by the fan-shaped x-ray beams in CT scanners, photons passing
through peripheral regions of the body at the edge of the fan-beam will not pass through as
much tissue as those transmitted through the centre. Therefore, the x-ray beam intensity fromthe peripheral regions would potentially be much greater and this would create a large dynamic
range in intensity at the detector, as well as giving higher radiation doses to superficial tissues.
Therefore, beam shaping filters that are thicker towards the edge having a cross-section similar
to that of a bow-tie, after which they are named, are placed in front of the beam. Bow-tie filters
reduce beam intensities at the periphery to match the greater attenuation at the centre of thebody, producing a more homogeneous distribution of radiation within the body and so give
better uniformity of noise within the image (Boone, 2009). The shape and composition of thefilters varies with vendor and some vendors have multiple bow-tie filters that can be selectedby the user, so it is important that the filter is matched to the body region being imaged. The
field of view used for head examinations will be smaller and the shape of the bow-tie filter
narrower than that for the body.

1805

4.2.4. Helical scanning, pitch, and beam collimation

1806
1807
1808
1809
1810
1811
1812
1813
1814
1815
1816
1817
1818
1819
1820
1821

(180) CT scanners have a matrix of detectors registering x-rays from the fan beam geometry
across the circumference of the gantry (providing the data required to reconstruct an image ofa slice through the patient), and along the scanner z-axis to allow multiple slices to be imaged
simultaneously. The x-ray beam is collimated so that it is incident on the required width of thedetector array along the z-axis (e.g. N detectors of thickness T). The patient couch is moved
through the CT gantry, so the x-ray beam follows a helical path around their body, collecting
data continuously. If the couch moves through a distance l along the z-axis during one tube
rotation, and this is equal to the width of the x-ray beam along the z-axis (NT), the pitch p ofthe helical scan (p=l/NT) is 1.0. Helical CT scans require interpolation between data fromdifferent projections along rotations during image reconstruction (Fig. 4.2). For CT scanners
in which the tube current is set manually, increasing the scan pitch could in principle reduce
patient dose, if the tube current remained constant, but all modern CT scanners have an ATCM
function to give a selected level of image quality (Section 4.4), and when this is used pitch has
little effect on patient dose (Ranallo and Szczykutowicz, 2015). However, larger pitch values
will give greater additional exposure from overranging for scanners without dynamic
collimation (Fig. 4.2).
61

DRAFT REPORT FOR CONSULTATION: DO NOT REFERENCE

1822
1823
1824
1825
1826
1827
1828
1829
1830

(181) Some CT vendors use an ‘effective mAs’ equal to the mAs divided by the pitch. Whenthe operator sets an effective mAs, the variation of pitch is compensated by changing tube
current or rotation time to maintain the same image quality. A lower pitch or a longer rotation
time can provide an option for imaging larger patients by enabling larger effective mAs values
to be used. However, both will increase the scan time which may create a challenge in fasterscans, e.g. in chest region and arterial phase scans where the biokinetics are rapid and there
may be a risk of losing the period of optimal enhancement. For paediatric scanning, where thepatient size is smaller than in adults, the gantry rotation speed is often set at 0.5 seconds todecrease the chance of motion artefacts.

1831
1832
1833
1834
1835
1836
1837

Fig. 4.2. Examples showing the CT beam trajectory for scans with different pitches. The
additional partial rotations at the start and end of the scans are required for image reconstruction.
Additional parts of the body not being imaged, highlighted by a darker shade, will be irradiated
if there is no dynamic collimation. The additional exposure is referred to as overranging and isgreater for larger pitches (e.g. pitch above 1.5). The applied pitch may be more than 3.0 withdual-source CT scanners. (Colin Martin, University of Glasgow).

1838

4.3. Image reconstruction

1839
1840
1841
1842
1843
1844
1845
1846
1847
1848
1849
1850
1851
1852
1853
1854

(182) Filtered back projection (FBP) is the analytical method used that has long been used
for reconstructing CT images. In essence this comprises back projection of all the profiles
collected at the respective angles and accumulation of the data in an image matrix. However, ahigh-pass mathematical filter must first be applied to the data, in order to provide acceptablecross-sectional images and to avoid degradation of details. FBP enables images of adequate
quality to be reconstructed rapidly for viewing. But the images tend to have high noise levels,
although this depends on the filter kernel used, and poor low-contrast detail detectability insome clinical situations, as well as being prone to artefacts. Filter kernels used in FBP arevendor-specific and typically cover a set of filters ranging from smooth to sharp image
representation. Choice of the appropriate filter is important for providing the type of image
required for each specific clinical application.
(183) Iterative reconstruction (IR) methods are proprietary techniques that are available inmodern scanners as additional image reconstruction and enhancement methods. In the IR
process, an initial image is produced that may be through FBP. Then, simulated raw-data
projections are computed in forward-projection using this image. These simulated projections
are then compared with the original measured raw-data to build a correction term based on the62

DRAFT REPORT FOR CONSULTATION: DO NOT REFERENCE

1855
1856
1857
1858
1859
1860
1861
1862
1863
1864
1865
1866
1867
1868
1869
1870
1871
1872
1873
1874
1875
1876
1877
1878
1879
1880
1881
1882
1883
1884
1885
1886
1887
1888
1889
1890
1891
1892
1893
1894
1895
1896
1897
1898
1899
1900
1901
1902

differences. A new image is then created through back-projection of a correction term. The
process goes through a number of iterations and depending on the modelling accuracy(especially in the forward-projection) may require high computing power. Most IR techniques
enable the noise level in images to be reduced and help to suppress artefacts.
(184) The primary aim of IR is to lower the noise level in the images. The operator has two
choices when IR is available: to scan at the same original dose (as established for the protocol
with FBP) obtaining better image quality (less noise and fewer artefacts) or to scan at a lower
dose but aiming to achieve an image quality equivalent to that from the FBP reconstruction(Hara et al., 2009). The potential for dose reductions of tens of percentages have been reported
in the literature depending on the scan protocol and CT vendor (Willemink et al., 2013b;
Morimoto et al., 2017; Mello-Amoedo et al., 2018; Zhang et al., 2019).
(185) If a scanner has the facility for IR, it should be used when it can improve radiologicaloptimisation by reducing radiation exposure while maintaining adequate clinical image quality
and reducing structured noise artefacts. Vendors offer options with different strengths or levelsof IR basically giving more or less noise reduction. Evaluation of IR options requires detailed
analysis of task-based performance, as well as spatial resolution and noise magnitude andtexture (AAPM, 2019b).
(186) Iterative reconstruction (IR) users need to be aware that these methods may causechanges in image texture leading to a blotchy appearance (Leipsic et al., 2010), although thismay not be an issue with more recent algorithms. Higher iteration strengths may cause changes
in image texture and a reduction in low contrast resolution (Prakash et al., 2010; Schindera etal., 2013; Willemink et al., 2013a).
(187) Radiologists accustomed to FBP images may initially find the unfamiliar appearance ofIR images off-putting and question their diagnostic accuracy. The settings (IR level andreconstruction filters for each clinical protocol indication) should be agreed by the radiologists
at the facility, and any modification in the level of IR and adjustments in exposure level should
be made in stages to ensure that radiologists interpreting the images are deriving a benefit fromthe changes made.
(188) Deep learning-based image reconstruction or restoration (DLIR) has emerged as
an alternative to FBP and IR. As deep learning is a subset of machine learning, DLIR can also
be classified as artificial intelligence (AI) based CT image reconstruction. DLIR seeks to solve
similar image reconstruction problems to IR, namely to enhance image quality by lowering thenoise level and reducing artefacts while preserving spatial resolution and contrast appearance(Singh et al., 2020; Arndt et al., 2021; Mohammadinejad et al., 2021). With fastercomputational speeds, this combination has significant potential and some vendors also offerdifferent flavours of DLIR adapted to anatomical part or several reconstruction levels, similar
to IR. An example of the traditional FBP, DR and DLIR from the same raw-data in CT is shownin Fig. 4.3.
(189) However, all new reconstruction methods and all new techniques together should beappropriately validated for the clinical indication. The precautions related to clinical validation
are important because these new methods carry non-linear characteristics which render themmore complicated than traditional FBP. DLIR methods are usually trained in the factory,
potentially with cohorts of patients that may not fully represent the local patient cohorts ordisease prevalence in the region. A local validation period is recommended during which raw
data is reconstructed with the settings used as standard in the clinic in parallel with DLIR for aselected patient group. The validations should be carried out on a variety of patients withvarying scan parameters. Analysis of the images by the radiologists and core team at the
inception can help the successful implementation of these new reconstruction methods.

63

DRAFT REPORT FOR CONSULTATION: DO NOT REFERENCE

1903
1904
1905
1906
1907
1908
1909
1910
1911

Fig. 4.3. An example of A) traditional (FBP; standard filter), B) iterative reconstruction(ASiR-V 50%) and C) deep-learning based reconstruction (TrueFidelity High) from the sameraw-data in a neurological brain scan performed with GE Revolution CT for a 5 years old girl.
The scan was performed with single 0.35 s axial rotation with 16 cm z-coverage, 120 kV,
0.625 mm slice thickness, CTDIvol of 20.7 mGy, and DLP of 330 mGy cm. The backgroundnoise values (SD in HU) in the images were 9 HU in A, 6 HU in B, and 3 HU in C. Images
courtesy of Mika Kortesniemi, HUS Medical Imaging Center, New Children’s hospital,
Helsinki, Finland.

1912

4.4. Automatic tube current modulation (ATCM)

1913

4.4.1. How it works

1914
1915
1916
1917
1918
1919
1920
1921
1922
1923
1924
1925
1926
1927
1928
1929
1930
1931
1932
1933
1934

(190) For a given tube potential, the tube current determines the number of photons emitted
and so the dose to the patient. A major technological development to aid in optimisation of CT
has been the inclusion of facilities to modulate the tube current automatically to take accountof variations in the attenuation of patients’ body tissues (Kalra et al., 2004; McCollough et al.,2006). These allow both for differences in patient size and for variation in tissue attenuation.
ATCM or automatic exposure control (AEC) is designed to maintain a similar level of image
quality throughout a scan and can reduce doses to individual patients by 30%–60%, when usedeffectively (Mulkens et al., 2005; Rizzo et al., 2006; Lee et al., 2008; Söderberg and
Gunnarsson, 2010). The tube current is varied as the scan progresses along the length of thepatient (z axis) with higher levels used for the thicker lateral shoulder and hip regions, and thecurrent reduced where the soft tissue attenuation is lower in the neck, thorax and lower
extremities. In addition, the tube current can be varied as the x-ray tube rotates around thepatient with the smaller diameter AP/PA directions receiving lower exposures than the lateral.
(191) CT operators need to be aware of how ATCM systems operate and understand concepts
on which they are based, as these are not intuitive, and the image quality references on which
exposure adjustments are based vary between CT vendors (Söderberg and Gunnarsson, 2010;
Sookpeng et al., 2014, Merzan et al., 2017). Generally, for the ATCM, the attenuation along thepatient is determined from the pre-imaging SPRs (one or two directions). The attenuation
values averaged over the SPR image are then used as the basis for setting the mA automaticallyfor each rotation to achieve a selected image quality reference using proprietary algorithms(Mayo-Smith et al., 2014). The SPR requirements for ATCM planning vary with CT vendor,
64

DRAFT REPORT FOR CONSULTATION: DO NOT REFERENCE

1935
1936
1937
1938
1939
1940
1941
1942
1943
1944
1945
1946
1947
1948
1949
1950
1951
1952
1953
1954
1955
1956
1957

and optimum selection for the scanner should be established during commissioning.
(192) In order to operate an ATCM system a parameter related to image quality must be
chosen that can be used as the reference for controlling tube current. The choice of the image
quality reference parameter has an important bearing on operation of ATCM systems and CT
scanner vendors and/or models have slightly different approaches to this.
(193) Noise level can be used as the simplest surrogate for image quality in radiologicalimages (Sookpeng et al., 2014). However, anatomical structures in larger patients tend to havehigher contrast due to the visceral fat, which facilitates the recognition of organ margins. As aresult, a higher level of noise can be tolerated when viewing images of larger patients (Wilting
et al. 2001). However, detection of low-contrast lesions (e.g. liver tumours) will require asimilar level of noise in thin or obese patients. The image quality references used by ATCM
systems can be either a level of image quality for a standard patient or relate to the noise levelin the image depending on the vendor (Martin and Sookpeng, 2016; Merzan et al., 2017).
(194) For scanners in which the operator chooses an image quality reference related to a
standard patient, the dimensions from the SPRs are compared with those for the standard
patient. The mA is adjusted according to predetermined levels with the strength of modulation
being chosen by the operator and the noise level in the image is allowed to change moderately
with patient size (Stratis et al., 2013; Wood et al., 2015; Söderberg, 2016). For scanners thatuse a noise index based on the standard deviation (SD) as the image quality reference, ATCM
systems seek to maintain the same noise level throughout a scan, a higher noise level may be
acceptable for larger patients to take account of differences in contrast between patients ofvarying size.

1958

4.4.2. Using ATCM and automatic tube voltage selection (ATVS)

1959
1960
1961
1962
1963
1964
1965
1966
1967
1968
1969
1970
1971
1972
1973

(195) Recent scanners have ATVS systems that calculate patient-specific mAs curves fordifferent tube potential levels based on the scan range, patient anatomy, and the contrast
required. An optimised tube potential can then be selected for the patient protocol, while themA is modulated during the scan for that tube potential with ATCM.
(196) Because ATCM systems from the various vendors use different control parameters,
translation of established protocols between scanners of different type is very difficult. Clinicalprotocols must never be blindly transferred between CT scanners without adjustment, unlessthe CT scanners are identical models and running identical functional versions of system
software. The user can try to set up equivalent protocols by selecting a variable such as the
CTDIvol (or preferably SSDE) and noise, preferably extending to image texture evaluation andmatching, through which to characterise the scanning protocols for patients (or phantoms) ofdifferent sizes. The AAPM CT protocols provide vendor and software specific examples to use
for common clinical indications (AAPM, 2022), Steps for translating ATCM settings in clinicalprotocols between CT scanners have been described in a number of studies (McKenney et al.,2014; Martin and Sookpeng, 2016; Sookpeng et al., 2017).

65

DRAFT REPORT FOR CONSULTATION: DO NOT REFERENCE

1974
1975
1976
1977
1978
1979
1980
1981
1982
1983
1984
1985
1986

Fig. 4.3. Plots showing examples of the variation in tube current along the bodies of twopatients, derived from ATCM operation for which noise has been used as a reference. A)
represents a small patient for whom the minimum mA may have been set a) too high restricting
the modulation (bold dashed curve), b) at an acceptable level (bold solid curve), and c) too low
allowing the tube current to fall to a level whether the image quality may be compromised (finedashed curve). B) represents a large patient for whom a) the maximum mA setting is too low
restricting modulation (bold dashed curve), b) at an acceptable level (bold solid curve), and c)
may be too high so that the mA and the dose may rise to an unnecessarily high level (finedashed curve). Judgements about the maximum and minimum settings that are appropriate
should be based on the requirements for image quality. The bands of mA between the shaded
areas represent the range over which tube current would be varied if no limits were set (Colin
Martin, University of Glasgow).

1987
1988
1989
1990
1991
1992
1993
1994
1995
1996
1997
1998
1999
2000
2001
2002
2003
2004
2005

(197) In certain scanners, limits can be set through the ATCM systems on the maximum andminimum tube currents to avoid the dose level rising too high or image quality being too
poor respectively. In scanners that use an image quality reference related to a standard patientor reference mAs, the limiting mAs values may be set automatically according to patient size.
But for scanner models that use a noise reference, the maximum and minimum mAs settings
can be selected by the operator (Fig. 4.3).
(198) Setting of wide limits of tube current may be acceptable for many patients. Example
plots showing how the tube current might vary as the scan moves along different patients, andthe impact of the limits on tube current are shown in Fig. 4.3. The tube current limits can be
set to ensure that doses for small patients are maintained at a high enough level to ensure
reasonable image quality (Fig. 4.3A) and doses for large patients are not excessively high (Fig.
4.3B), but if limits are too restrictive this will curtail ATCM performance. The maximum mAlimit can also be set to allow scans to be performed with a small rather than a large focal spot
on some scanners in order to achieve better resolution.
(199) The number of photons contributing to an image depends on image slice thickness.
Scanners with a reference slice thickness linked to mAs, will give a different noise level when
the image slice thickness is changed (Sookpeng et al., 2015; Merzan et al., 2017), but forscanners using an image reference linked to noise, a reduction in the image slice thickness used
for acquisition will be accompanied by a corresponding increase in mAs to maintain the same66

DRAFT REPORT FOR CONSULTATION: DO NOT REFERENCE

2006

noise level in older scanners (Sookpeng et al., 2015).

2007

4.4.3. Position the patient and QC testing for ATCM systems

2008
2009
2010
2011
2012
2013
2014
2015
2016
2017
2018

(200) The projected patient size in AP/PA direction SPR depends on the vertical centring of
the patient. If the patient is nearer to the x-ray tube, the SPR image will be magnified, whereas
if they are nearer to the detector, the SPR image will be smaller (Matsubara et al., 2009,
Supanich, 2013) (Fig. 4.4). Since the ATCM calculations are based on an assumption that thepatient is centred within the gantry, tube currents selected by the ATCM may be higher or lower
if a patient is mis-centred. This issue has been addressed through automatic adjustments in thelatest CT models of some vendors (Zhang and Ayala, 2014). Some modern systems allow forsmall lateral displacements of the table from the console to compensate for patient mis-centring.
Lateral displacement can create a similar effect but this does not typically present a problem.
The influence of the SPR on ATCM and also ATVS has been evaluated by using phantoms(Kaasalainen et al., 2019) and with patients (Filev et al., 2016).

2019
2020
2021
2022

Fig. 4.4. Diagrams showing how height of the couch can affect the apparent patient dimension
on an SPR recorded with a PA projection. When patients are lower (left) the image is magnified,
while when they are higher (right) the image is reduced. (Colin Martin, University of Glasgow).

2023
2024
2025
2026
2027

(201) Testing of ATCM systems should involve phantoms with both discrete and continualchanges in phantom diameter and net attenuation (AAPM, 2019b) e.g. by using separate
phantoms or with specific ATCM phantoms with combinations of sections (Sookpeng et al.,2013; Wilson et al., 2013; Merzan et al., 2017; Sookpeng et al., 2020). These allow the variationin noise level and tube current with phantom dimension, linked to CTDIvol, to be evaluated.

2028

4.4.4. Organ dose modulation

2029
2030
2031
2032
2033
2034

(202) Another feature incorporated into new CT scanners is a facility to reduce the mA to theanterior aspect of the body in order to minimise doses to radiosensitive organs such as thebreasts, thyroid, and eye lenses. These options, called variously organ dose modulation, organbased tube current modulation (DM) or organ effective modulation by different vendors, reduce
tube current typically between 90 and 180 on the anterior aspect where the radiation isincident on the sensitive organs (Kim et al., 2013; Akai et al., 2016; Lambert and Gould, 2016;
67

DRAFT REPORT FOR CONSULTATION: DO NOT REFERENCE

2035
2036
2037
2038

Kotiaho et al., 2018; Ota et al., 2019). The tube current in the remainder of the rotation may be
increased so that the overall radiation dose (CTDIvol) remains constant (Hoang et al., 2012),
or an increase in noise level in the image with a lower dose may be accepted (Dixon et al.,2016).

2039

4.5. Other CT technology and procedures

2040

4.5.1. Dual-energy CT

2041
2042
2043
2044
2045
2046
2047
2048
2049
2050
2051
2052
2053
2054
2055
2056
2057
2058
2059
2060
2061
2062
2063
2064
2065
2066
2067

(203) If simultaneous images can be obtained using different energy spectra, tissues canpotentially be characterised or classified based on information about their differences inattenuation (Johnson et al., 2007). There are basically five methods being applied to modern
CT scanners (incorporating energy integrating detectors) achieving this ‘spectral energy’ or
dual-energy CT (DECT) scanning. Scanners may 1) have two x-ray sources; 2) use a single xray-source with fast switching of tube potential; 3) use a single-source CT that switches tube
potential between gantry rotations; 4) use a single-source CT that splits the incident beam into
two halves with different filtration and separate detection in the longitudinal (z) direction, or 5)
a single source used with two superimposed detectors separated by a filter, so that different
energy spectra are incident on the second detector (McCollough et al., 2015; D’Angelo et al.,2019).
(204) Where two tube potentials are used in DECT, these are typically 140–150 kV (withadditional filtration in dual-source models) and 80–100 kV and dose levels are similar to thosefor single-energy CT (Schenzle et al., 2010; Sodickson, et al., 2021). DECT can provide anumber of potential improvements for imaging investigations. These include CT angiography
with removal of overlying bone which has different energy attenuation characteristics fromiodine (Schulz et al., 2012), organ perfusion and blood pool imaging can be carried out (Zhang
et al., 2013; Sun et al., 2018), and characterisation of structures such as urinary stones (Qu etal., 2013). There is also the possibility of generating a ‘virtual’ non-contrast set of images (Fig.
4.5) from a single scan with contrast to avoid a pre-contrast scan (Graser et al., 2009; Barrett
et al., 2012; George et al., 2017; Rajendran et al., 2021b).
(205) Comparisons suggest that DECT can provide better image quality with comparable orslightly lower doses than conventional CT (Fang et al., 2018). However, the spectral separation
remains a challenge and providing sufficient photon energy differentiation for image
reconstruction can be a limiting feature, although various technical solutions are applied indifferent DECT scanner models. More information on current models, clinical applications anddosimetric considerations is contained in an AAPM report (McCollough et al., 2020).

68

DRAFT REPORT FOR CONSULTATION: DO NOT REFERENCE

2068
2069
2070
2071
2072
2073
2074
2075
2076

Fig. 4.5. Images from a photon counting detector (see 4.5.7) DECT to achieve 66 ms temporal
resolution. Axial CT images are shown on the left and oblique coronal images on the right. The
multi-energy capabilities allow creation of virtual monoenergetic images (VMIs), which show
increased iodine signal (mean HU in the regions of interest). The VMIs added to the inherently
higher iodine CNR and provided clearer delineation of the left coronary artery (right hand
images). The white arrow in the bottom right image indicates calcification of the aortic valve.
90 ml iohexol contrast was used which was 18% less than for single kV images. (Rajendran etal., 2021b; with permission from RSNA.)

2077
2078
2079
2080
2081
2082
2083
2084
2085

(206) As a summary of the image data point-of-view, spectral imaging with dual-energy orspectral detectors offers additional image representations for diagnostics. These include virtual
monochromatic (specific keV level) images, which show increased iodine signal compared toconventional IED CT (Fig. 4.5). DECT also enables the formation of iodine concentration maps
and virtual non-contrast images excluding highlighting of iodine filled vessels in contrast
enhanced scans (Fig. 4.6), and effective Z images which widens the diagnostic value andoptimisation role in CT imaging. In order to gain the full potential from spectral imaging,
related clinical applications are essential to manage the diagnostic review process andradiologist workload with the increasing CT data sets.

69

DRAFT REPORT FOR CONSULTATION: DO NOT REFERENCE

2086
2087
2088
2089
2090

Fig. 4.6. Images derived from the scan data in Fig. 4.5, showing iodine maps with concentrationin mg ml-1 and the virtual-non-contrast mages used to visualise calcifications having a similarattenuation to the iodinated blood (white arrow bottom right). (Rajendran et al., 2021b; withpermission from RSNA ).

2091

4.5.2. Cardiac and coronary CT

2092
2093
2094
2095
2096
2097
2098
2099
2100
2101
2102
2103
2104
2105
2106
2107
2108
2109
2110
2111
2112
2113
2114
2115
2116
2117

(207) Studies of the heart and coronary arteries have become common with broader fan beams
and faster acquisition times. There are several ways they can be performed (Montalescot et al.,2013). Depending on the scanner model, the x-ray beam can be run with a single wide-beamaxial scan or continuous helical scan, while the patient is translated through the gantry at a slow
speed with a small pitch and images reconstructed retrospectively for one or more phases of
the cardiac cycle. More dose efficient methods set up the scanner prospectively to trigger
sequential or faster helical scans at a pre-selected phase of the cardiac cycle determined by theheart rate from the ECG (Husmann et al., 2008; RCR, 2014) and images reconstructed fromdata combined over multiple cycles or motion-corrected sinogram data. This may require
pharmacological support to slow and steady the heart rate and is more challenging in the infant
and young child. X-rays at full intensity are then only emitted during the phases required for
imaging, reducing the dose significantly (Alhailiy et al., 2019). The techniques can provide
good image quality at a relatively low dose mainly for non-obese patients with low and stable
heart rates (Achenbach et al., 2010).
(208) The acquisition is usually performed during the diastolic phase to minimise motion
artefacts. However, if the pulse rate is above 70, end-systolic phase reconstruction may provide
a better temporal window to freeze the cardiac movement as compared to the diastolic phase(Ruzsics et al., 2009; Hassan et al., 2011). Increasing the length of the scanning time, prior toand after the selected phase of the cardiac cycle being imaged (referred to as padding), can beused to increase the window for reconstruction which may be used to improve diagnostic
accuracy or to provide a range of cardiac phases for image reconstruction. However, any
increase in padding time will increase the radiation dose (Alhailiy et al., 2019).
(209) Cardiac-specific CT scanners are sufficiently wide to encompass the whole cardiac
volume, in order to image the heart in a single rotation. A review of ECG gated studies
concluded that low tube voltage protocols could substantially reduce doses for smaller patients,
while still producing good image quality (Tan et al., 2018). Increases in image noise at lower
70

DRAFT REPORT FOR CONSULTATION: DO NOT REFERENCE

2118
2119
2120
2121
2122
2123
2124
2125
2126
2127
2128
2129
2130
2131

voltages were offset by the increase in vessel contrast enhancement.
(210) Additional benefits may be obtained from the use of advanced image reconstruction,
deep learning, and related noise reduction. High resolution photon-counting CT (see Section
4.5.7) can demonstrate coronary artery plaques and stent narrowing with better spatial
resolution and fewer artefacts than conventional CT (Rajagopal et al., 2021). Rapid
advancement in CT myocardial perfusion imaging allows for (a) the identification ofhemodynamically significant coronary artery disease, (b) CT delayed-enhancement imaging todetect myocardial scar after myocardial infarction, and (c) measurement of the extracellularvolume fraction in non-ischemic cardiomyopathy (Ko, 2019). Paediatric heart rates often
remain relatively high, despite pharmacological heart rate reduction (Mortensen and Tann,2019). However, dual source and wide beam techniques that allow cardiac scans to be obtainedin sub-second, single rotations can be used for paediatric patients without the need for sedation.
Looking at the overall perspective, the possibility of avoiding sedation with children is
extremely valuable, improving the overall clinical process and patient safety.

2132

4.5.3. CT perfusion studies

2133
2134
2135
2136
2137
2138
2139
2140
2141
2142
2143
2144
2145
2146
2147
2148
2149
2150
2151

(211) CT perfusion involves a series of intermittent CT acquisitions to determine functional
haemodynamic parameters such as blood flow, blood volume, mean transit time, and time topeak enhancement (Hoeffner et al., 2004). In addition to cardiac perfusion CT, brain CT
perfusion is another primary use, applied for assessment of stroke, but a similar technique may
be employed for both brain and body tumour characterisation and assessment of tumour
response to treatment, and other inflammatory and vascular conditions. When performing CT
perfusion studies, it is essential to keep the tube voltage low (70 or 80 kV) to reduce radiation
dose. These CT techniques have provided new insights into pathophysiology of cancer, stroke,and other diseases such as pulmonary hypertension and provide quantitative ‘omic’ data.
However, examples of skin injury and hair loss from early applications of CT brain perfusioncases in the USA have occurred (ICRP, 2007a). These have involved errors due to use ofincorrect settings by operators who did not understand the potential impact of CT parameterchanges on dose.
(212) Procedures with the potential to cause injury should be identified beforehand and steps
taken to ensure all settings are satisfactory. Checks can be made on skin dose levels, since the
CTDIvol displayed on the scanner console is similar to the surface skin dose for head scans,while for body CT scans, the surface skin dose is about 1.3 × CTDIvol (Martin et al., 2017). A‘CT Dose Alert’ standard (AAPM 2011b; NEMA, 2013) introduced an alert function to CT
scanners to avoid inappropriately high doses (Mahesh, 2016).

2152

4.5.4. CT fluoroscopy and guided interventions

2153
2154
2155
2156
2157
2158
2159
2160
2161
2162

(213) CT fluoroscopy is now used to guide interventions combining cross-sectional images
or 3D image volumes with almost real-time display. Images at a fixed position are continually
updated providing additional depth information for guiding biopsies and fluid drainage,
allowing finer needle control. The technique requires an operator panel for controlling table
movement and exposure factors, with exposure usually being activated via a foot-pedal switch.
(214) Tube currents of a few tens of mA are used, giving incident doses of 2–10 mGy s-1,
which are higher than in interventional fluoroscopy. While infrequent, CT interventions may
result in relatively high radiation exposures (Arellano et al., 2021). Care is required inmonitoring the potential skin dose, as imaging for guidance of a needle, catheter, or probe may
be repeated in a similar location (Teeuwisse et al., 2001, Tsalafoutas et al., 2007).
71

DRAFT REPORT FOR CONSULTATION: DO NOT REFERENCE

2163
2164
2165
2166

(215) Radiologists can potentially receive significant radiation doses to their hands, which
will be close to the scan plane during image acquisition as they manipulate biopsy needles.
Operator lead screens and aprons are part of appropriate worker protection in CT fluoroscopy
as in interventional radiology settings. (Buls et al. 2002; ICRP, 2018b).

2167

4.5.5. Photon counting CT

2168
2169
2170
2171
2172
2173
2174
2175
2176
2177
2178
2179
2180
2181
2182
2183

(216) Photon-counting CT (PCCT) is a new addition to clinical CT technology with thepotential both to improve performance in existing CT imaging techniques and provide novel
diagnostic applications (Taguchi and Iwanczyk, 2013; Flohr et al., 2020). In contrast toconventional, integrated energy detector (IED) CT, PCCT systems use energy-resolving x-ray
detectors that register interactions of individual photons, including the energy deposited. This
allows an approximate energy spectrum to be recorded based on energy thresholds, whereas
the conventional IED CT technology records the integrated signal intensity from a large
number of photons, but with a range of energies (Persson et al., 2016; Flohr et al., 2020).
(217) The potential advantages of PCCT imaging include improved SNR, exclusion ofelectronic noise, improved spatial resolution, lower patient doses, correction of beamhardening artefacts, and the ability to distinguish multiple contrast medias. This could allow
use of alternative contrast media and create opportunities for quantitative imaging. PCCT
scanners are already in clinical use, and have shown potential for dose reduction also in specificscanner designs such as in cardiac and breast imaging (Kalender et al., 2017; Lell andKachelriess, 2020; Hsieh and Flohr, 2020; Eberhard et al., 2021). PCCT has the potential todramatically change practices in clinical CT imaging (Rajendran et al., 2021a).

2184
2185
2186
2187
2188
2189
2190

Fig. 4.7. Comparison of images from an IED CT scan (left) and a high resolution PCCT scan(centre and right) for a 74 y old male with multiple myeloma, acquired using the same dose
(4.2 mGy) and 2 mm slice thickness. The PCCT showed 47% lower noise (69.4 HU vs 36.8
HU) in the 2 mm images. Use of a 1 mm PCCT slice thickness gave a similar noise level to the
IED CT and improved delineation of the vertebral lesion (white arrow). (Rajendran et al.,2021b; with permission from RSNA).

2191

4.6. Development of clinical CT protocols

2192

4.6.1. Establishing clinical protocols

2193
2194

(218) All scans should be performed according to settings agreed and established at the startwhen a CT scanner is installed and commissioned, and these should then be reviewed and72

DRAFT REPORT FOR CONSULTATION: DO NOT REFERENCE

2195
2196
2197
2198
2199
2200
2201
2202
2203
2204
2205
2206
2207
2208
2209
2210
2211
2212
2213
2214
2215
2216
2217
2218
2219
2220
2221
2222
2223
2224
2225
2226
2227
2228
2229
2230
2231
2232

revised periodically. The protocols should be developed with input from consultant
radiologist(s), lead CT radiographer(s) / technologist(s), and the medical physics expert, withrecommendations from the company applications specialist. Initial protocols should be set up
for examinations that are performed frequently and for the most urgent indications. Values ofprotocol parameters more commonly used should be set first to lay the basis for subsequentparameter settings. The level of image quality, exposure factors, slice thickness, pitch, filters,
and the need for iterative or deep-learning based reconstruction should be agreed among theprofessionals involved. The optimisation of protocols for paediatric and pregnant patients are
considered separately in Sections 5 and 6. The AAPM have developed a set of protocols for
specified diagnostic tasks that can be accessed via the internet (AAPM, 2022).
(219) Protocol optimisation should be based on consistent CT scan protocol naming andcoding. Thus, the organisation with multiple CT sites may implement harmonised imaging
protocols which can be identified unequivocally based on the protocol name and code. Some
vendors have developed protocol management features into their software tools which enable
protocol data from scanners to be pulled for centralised review and comparison, protocol
version handling and even distribution of revised protocols to interoperable scanner models.
This will greatly assist successful protocol management in larger, multi-site organisations.
(220) Optimisation of any radiological x-ray modality should be based on the proper
limitation of exposure range to only the area based on clinical indication and the correctly
defined field-of-view (FOV). The level of image quality required should be agreed among theprofessionals involved. Some of the factors and relationships that should be considered whensetting up protocols are summarised in Boxes 4.3 and 4.4.
(221) Input is required from all radiologists to determine image quality requirements (Mauéset al., 2018). There should be consensus amongst radiologists within a department with regard
to the clinical protocols for each application. Different dose protocols for individual
radiologists are not justified and can lead to errors and unnecessary dose variation. The aim
should be to create a single standard examination protocol suitable for the clinical task. This
could be feasible with the lead-radiologist for each organ/body part being the person-in-chargeof the corresponding organ-area specific protocols and collaborating with the other radiologists,
radiographers and medical physicists involved. Ideally, there are ongoing interactions with theclinical referrers (e.g. specialty conferences) and managers to optimise protocols, andcommunication with patients and their families to improve health literacy.
(222) Whether or not a scan with contrast is required will depend on the clinical questions tobe answered. Some patients will only require a single scan (particularly children), but others
will require several with pre-enhancement and post-enhancement during the arterial or venous
phases. The possibility of using DECT, if available, should be borne in mind, as this can
produce virtual non-contrast images without extra phases. Timing of contrast bolus by using
bolus tracking or applying a test bolus will also be important for obtaining satisfactory images.

2233
2234
2235
2236
2237
2238
2239
2240
2241
2242

(223) Exposure factors should be individualised through use of the ATCM to adjust dose forpatient size, although it may be necessary to have separate technique charts or protocols forparticular patient cohorts e.g. such as different age groups (preferably by size in terms ofdiameter) for paediatric patients, and for small, average, large, and obese patients (Box 4.2).
As different clinical questions require different diagnostic approaches, there should be a
sufficient number of indication-specific CT scan protocols established, easily available, andproperly maintained in order to have a more efficient and comprehensive optimisation processin CT. Overall optimisation of CT scan protocols should be managed in a larger context byintegrating this action into daily clinical routine. In multi-site and multi-scanner organisations
certain anatomical or organ range protocols could be managed by that organ specific radiology
73

DRAFT REPORT FOR CONSULTATION: DO NOT REFERENCE

2243
2244
2245
2246
2247
2248
2249
2250
2251
2252
2253
2254
2255

team in order to agree and make adjustments to achieve consistent image quality target levels
for similar indications. Thus, the number of indication-specific protocols should reflect the trueneed for separate protocols in that organ range and these protocols should be kept undercoherent control. Likewise, the local or vendor specific expert teams (including technologists,
medical physicist, radiologist and vendor application specialist) may ensure that the multiple
protocols covering many organ ranges and indications are consistently maintained to reflect
the current capabilities of the scanner models and local patient flow process.
(224) Agreement in setting the initial protocols is just the start of this process. The practice
should then be benchmarked through dose surveys and assessments of image quality during
the early stages of implementation and regularly by QA activities and audits during normal
clinical use. For more information about the explicit CT protocol setting, web resources for
protocol data are available from professional medical organisations and medical physicist
organisations (e.g. AAPM, 2022; CTisus, 2022).
Box 4.3. Factors to be aware of when setting up CT scan protocols and scanning patients.
Pitch, mA, slice thickness and rotation time
•

•

•
•

•

•
•

Be aware of interactions between different parameter settings on your scanner e.g. how
ATCM is affected by changes in primary reconstruction slice thickness and reconstruction
kernel.
Compare results of new protocols with original ones, when making any changes. It is
recommended to keep a database with separated files recording the historical changes in
the protocols (acquisition and reconstruction parameters for each clinical protocol and foreach CT system in the hospital, which should be keep up to date regularly). These can be
handy when major changes or upgrades in systems take place and CT protocols need tobe reinstalled.
Know whether or not tube current remains the same or is varied automatically when pitch
is altered.
Volumetric acquisition mode using thin slices increases the image noise, but allows for
MPR review at thicker reconstruction and 3D visualisations. Thin slices benefit fromreduced contrast averaging by the partial volume effect.
Poisson statistics of image data acquisition: when acquisition slice thickness (or radiationdose) is halved, the noise will increase by a factor of 2. Note that the relationship withdose is not certain with more advanced reconstruction methods (IR and DLIR).
Proportionate reductions in patient dose can be achieved by reducing tube current, while
being careful not to compromise diagnostic information.
Techniques that increase scan time (lowering pitch, decreasing total collimation width orincreasing rotation time) may be problematic in certain contrast enhanced CT scans thatinvolve rapid biokinetic changes or chest imaging with the need for breath hold.

2256

74

DRAFT REPORT FOR CONSULTATION: DO NOT REFERENCE

Box 4.3. (Continued)
Tube potential (see Box 4.2)•••

A lower tube potential can improve contrast for smaller patients, and will reduce dose.
When imaging structures enhanced with contrast media, the iodine CNR can be used as
an approximate image quality metric to use for evaluating adjustments to tube potential
and mAs.
Automatic tube voltage selection (ATVS) systems calculate patient-specific mA curves
for different tube potential levels to allow an optimised tube potential to be selected

Patient set-up and plan••

Ensure that the patient is centred in the gantry before commencing an examination, as thismay affect operation of the ATCM and ATVS.
Use appropriate anatomical markers to define scan start and stop positions to ensure
consistency.

Iterative (IR) or deep learning (DLIR) reconstruction techniques
•
•
•
•

•
•

IR or DLIR are not themselves dose-saving techniques, but their use can enable exposure
factors to be reduced through improvements in image quality.
The dose reduction that can be achieved with IR or DLIR will depend on the clinical task.
Substantial dose reduction may be possible for imaging high contrast objects.
Vendors offer options with different strengths or levels of IR or DLIR giving more or lessnoise reduction. Determine which are appropriate for each application.
More aggressive noise reduction may be beneficial for detection of low-contrast
structures, but application of too high a strength may affect tissue texture and visualisationof low contrast lesions.
IR or DLIR strategies that improve spatial resolution or decrease artefacts, rather than
reduce noise, may be beneficial for CT angiography.
Measurements of the noise power spectra from phantoms can be helpful for interpretingchanges in the visual appearance of images generated with alternative reconstruction
methods.

2257

75

DRAFT REPORT FOR CONSULTATION: DO NOT REFERENCE

Box 4.4. Points to be aware of when setting up protocols (assumes ATCM use)
Setting up protocols for CT procedures is a crucial part of optimisation and some of the points
to be considered during this process are summarised here.
•
•
•
•
•
•
•

•

The choice of proper clinical image quality reference for specific indications is the primary
determinant of the dose to the patient
Understanding how the ATCM works with respect to the particular vendor for your CT
scanner is key to achieving proper operation and avoiding potential errors
Do not choose too high a mAs image quality reference or too low a noise reference for
operation of the ATCM
Establish a standard routine for performing the SPR linked to ATCM (and ATVS)
operation, following vendor recommendations to ensure that the image signal is adequate.
For scanners that use an image noise reference, the operator may need to select a higher
noise level for larger patients to avoid high patient doses.
Ensure that settings of maximum and minimum current, where they are determined by theoperator, are appropriate and do not unintentionally restrict mA modulation.
Scanning phantoms in the form of cones or sections with different dimensions provide a
useful method for understanding and monitoring of the ATCM operation.
Anthropomorphic phantoms can also be an alternative.
Organ dose modulation reduces tube current for angles where x-rays are incident on
sensitive organs (mainly eyes, thyroid and breast) and is an option on modern CT scanners.

2258

4.6.2. Patient dose audit

2259
2260
2261
2262
2263
2264
2265
2266
2267
2268
2269
2270
2271
2272
2273
2274
2275
2276
2277
2278
2279

(225) Insufficient feedback on dose (and image quality) tracking, may lead to a dose increaseover time or leave doses at a high level in order to ensure that image quality is good, despite
the potential of reduction using the available CT systems tools. The CTDIvol gives ameasurement of dose within a phantom of standard size (Box 4.1) and is suitable for dose
surveys and optimisation of practices. However, it is a poor reflection of doses to individual
patients of varying size and does not represent real morphology and anatomy; a size specificdose estimate (SSDE) has been developed to provide more information on doses to individual
patients (Box 4.1) Where dose information is contained in the DICOM header and Radiation
Dose Structured Reports (RDSR) for each examination, audits of patient doses are becoming
easier to perform (Annex B) (ICRP, 2022). Commercial dose monitoring systems orfunctionalities integrated into PACS/RIS software provide access to substantial amounts of data;
these systems provide an overview of the doses associated with particular examinations to beobtained more easily, as well as allowing comparisons between different CT scanners (Nicol etal., 2016). Recent systems also cover other relevant features of optimisation such as scan
protocol and scanner utilisation management features.
(226) There are older scanners still in use in developing countries that do not display CTDIvol
and DLP values (Rehani and Vassileva, 2018). Where this is the case the mAs, tube potential,
pitch, and scan length values should be recorded to provide an indication of any variation withtime. Measurements of CTDI100 in terms of mGy/mAs can then be used to derive CTDIvol and
DLP values for making comparisons and use in development of protocols (Section 4.6.1).
(227) Median values of dose quantities derived from survey data can be compared with DRLs
76

DRAFT REPORT FOR CONSULTATION: DO NOT REFERENCE

2280
2281
2282
2283
2284
2285
2286
2287
2288
2289
2290
2291
2292
2293
2294
2295
2296
2297
2298

(ICRP, 2017, 2022). The form in which data are presented, for example using boxplots or bar
charts to compare results with the regional or national DRLs, can assist local staff inunderstanding the level of optimisation that has been achieved.
(228) If local median values are higher than the DRLs, the protocols, techniques, and image
quality should be reviewed. There are many possible reasons why median values of dosequantities may be higher or lower than the DRL. First of all, the calibration of the values
displayed in the scanner should be checked to see if they are realistic. Then, the clinical imaging
task for which the DRL value has been established should be similar to the one being studied,with similar patient cohorts and patient weight ranges. Finally, a check should then be made as
to whether the DLP and CTDIvol are both high, as this can be informative in determining
possible causes. It should be noted that, even if doses are lower than the DRL, this does notmean that further optimisation is not possible or should not be undertaken.
(229) The following paragraphs discuss possible causes of higher doses and Table 4.1
summarises some of the possible causes linked to whether the CTDIvol and/or DLP are high.
An estimation of these parameters is usually available on the screen before a scan is performed
and can potentially enable a quick check of parameters to be made at this stage. If radiographers
are familiar with the range of appropriate values, they can then modify a protocol to avoid
delivery of an unnecessarily high dose to the patient. Whatever changes might be made, it ispivotal to ensure that the image quality remains adequate for the clinical task.

2299

Table 4.1. Possible causes of higher doses for trouble shooting dose audit results
Observed effects

2300
2301
2302
2303
2304
2305

Patient size

Things to check and possible causes

CTDIvol acceptable, but DLP
appears too high

Average

Check whether scan length is reasonable or multiple
scan series are included.

CTDIvol acceptable, but total
accumulated DLP appears too
high

Average

Check number of scan phases with and without
contrast being performed, and whether the number
is reasonable.

CTDIvol and DLP both high

Average

Review all major scan parameters, including e.g. kV,
mAs (or ATCM) level and thickness of firstreconstructed slice

CTDIvol and DLP both highfor body scan

Small

Is the displayed CTDIvol for a small field of view thatfor a head phantom rather than a body one

CTDIvol and DLP both high

AverageIs too low a noise level or too high an ATCM image
quality reference being selected?

CTDIvol and DLP both highLarge

Is too low a noise level or too high an ATCM image
quality reference being selected?

No tube current modulation
effects observed

Large orsmall

Check whether tube currents set for ATCM areappropriate, the maximum value for a large patientor the minimum for a small one. Also, check themodulation curves displayed, if they are available.

(230) If the DLP is high, but the CTDIvol is within the normal range, then the scanned region
may be longer than necessary. Another common reason for higher values for the DLP is the useof more scan series, as ones may be performed initially without contrast medium, followed byones enhanced with contrast. If this is the case consideration should be given to whether theseseries are all necessary for the clinical task being undertaken. It should be noted that the DRL
values apply to a single CT scan series and not to the cumulated DLP of the entire examination.
77

DRAFT REPORT FOR CONSULTATION: DO NOT REFERENCE

2306
2307
2308
2309
2310
2311
2312
2313
2314
2315
2316
2317
2318
2319
2320
2321
2322
2323
2324
2325
2326
2327
2328
2329
2330
2331
2332
2333
2334
2335
2336
2337
2338
2339
2340
2341
2342
2343
2344
2345
2346
2347
2348

(231) If both DLP and CTDIvol are high, then the scan parameters should be reviewed indetail to determine if they were justified or corrective actions needs to be taken. The ways inwhich controls influence patient dose and image quality for CT scanner models from thevarious vendors are different, so it is important that members of the core radiological teamunderstand how the settings on the scanner affect the imaging process (ICRU, 2012; AAPM,
2014).
(232) There may also be reasons why the CTDIvol displayed may not be the appropriate one.
For paediatric patients in particular, it is necessary to check that the CTDIvol value is theappropriate one for the body (referenced to a 32 cm diameter PMMA cylindrical phantom), as
if a small field of view has been selected, then the CTDIvol value may relate to a head scan
(referenced to 16 cm diameter PMMA phantom) for which the corresponding dose value isabout double (Box 4.1). For some older scanners operating under ATCM when systems werefirst introduced, the maximum value of the CTDIvol is displayed rather than the average oreffective one over a whole scan, which will again give overestimated results for the analysis.
(233) Assessment of doses for patients of standard weight is often insufficient for a full
assessment of scanners operating under ATCM, as there may be particular issues for scans oflarge or small patients, so it is informative to view the form of the distribution for all patients.
If patient size information is available, ideally measured from the scanner display, then dosequantities CTDIvol, DLP and optimally the SSDE can be plotted against patient diameter(Sookpeng et al., 2014; ICRP, 2017; Kanal et al., 2017; Boos et al., 2018; ACR-DIR, 2022).
The optimisation process includes various steps where more demanding analysis techniquesthat are provided by medical physicists or engineers are needed. The proper use andconfiguration of dose monitoring systems require dosimetry and statistical knowledge in order
to exploit their full potential in clinical use. When configuring and implementing dosemonitoring systems, it is important to verify that the DICOM and RDSR are activated and inuse whenever possible (Annex B), since these structured reports provide an extensive
description of radiation exposures for individual irradiation events. Also, the validation of dose
data provided to the dose monitoring system should be verified when new equipment is linked
up or updated. Continual improvement is a general quality management principle which isincluded in the international quality standards.
(234) There are many occasions where the routine optimisation actions should be
supplemented by more sophisticated physical dose and image quality assessments. Dosemonitoring results occasionally trigger questions where answers are not provided by simple
evaluation of exposure parameters. In such assessments, standard dose measurements related
to CTDI formalism can be supplemented by studies on anthropomorphic phantoms which inmany cases may give much more realistic dosimetry references for patient-specific dose
calculations and even allow for more advanced image quality assessment. Anthropomorphic
phantoms may be used in physical or computational form. In physical form, actual point-dose
measurements can be done in relevant radiosensitive organ locations in the phantom, to verify
the dose performance of the scanners with actual clinical protocols or some allow for theinsertion of ionisation chambers. Computational phantoms may be used in more elaborate dose
simulations to acquire organ dose estimates and 3D dose distributions. An example of suchMonte Carlo dose simulation, providing a 3D heat map of dose levels, is presented in Fig. 4.8.

78

DRAFT REPORT FOR CONSULTATION: DO NOT REFERENCE

2349
2350
2351
2352
2353
2354
2355
2356
2357
2358

Fig. 4.8. Example of highly heterogeneous 3D dose distribution at a coronal view resulting
from a helical chest CT scan performed on an anthropomorphic adult female model. Brighter
colours refer to higher absorbed doses in that specific position. Note the scattered radiation
which extends outside the primary scanned region. The stripe patterns indicate the helical beam
path during the scan. Dose has been calculated with Monte Carlo (MC) simulation, taking into
account the CT scanner x-ray source model and scan parameters. The colour bar dose scale has
been chosen to represent a typical and quite conservative dose level, and does not demonstrate
more modern low-dose settings that are available on new equipment. Image courtesy of Mika
Kortesniemi, HUS Finland.

2359
2360
2361
2362
2363
2364
2365
2366

(235) The benefits of anthropomorphic phantoms are that the whole scatter environment
provided by the human body can be included in the scan scenarios and dose assessments.
Physical and computational anthropomorphic phantoms may also be used for image quality
evaluations. Thus, dose and image quality characteristics may be studied in reference objects.
Such actions link the optimisation process to scientific research. Further information about
patient specific dosimetry is provided in the joint AAPM-EFOMP TG246 report (AAPM,
2019a) where this subject is extensively discussed with valuable reference data for medical
physicists.

2367

4.6.3. Subjective and continuous assessment of CT protocols: The core team and beyond

2368
2369
2370
2371
2372
2373
2374
2375
2376
2377
2378
2379

(236) The scan protocols once established should be reviewed periodically and changes
implemented as required. Protocol development should be a continuing process withmeasurements being made of the impact of changes and the whole process repeated. Whenchanges are made to clinical protocols, this should be discussed with all those involved. The
new protocol should be tested against the old one prior to use in patients, and depending on themagnitude of the changes, practical assessments on phantoms or simulations may be required
to evaluate changes in dose and image quality.
(237) Changes such as the introduction of iterative or deep learning reconstruction or
reductions in dose levels should be made in stages. Shortly after implementation, checks should
be made to confirm that the desired changes have been achieved and evaluations carried out toensure all radiologists interpreting the images find the changes acceptable. Then a dose audit
should be performed. The previously mentioned protocol management software and tools are
79

DRAFT REPORT FOR CONSULTATION: DO NOT REFERENCE

2380
2381
2382
2383
2384
2385
2386

currently emerging from different vendors in addition to the dose management software whichshould make consistent indication-specific protocol optimisation, version management andupdates easier for CT users. These automated methods are even more important when protocol
management is pursued in larger multi-site organisations with larger numbers of scanners andof established indication specific CT scan protocols. Guidance on the approach to practicaloptimisation is given in Box 4.5 and general arrangements that relate to facilities at different
levels in development of their optimisation strategy are set out in Box 4.6.
Box 4.5. Guidance for CT protocol development and maintenance
•
•
•
•
•
•
•

Standard clinical protocols should be agreed by the core team and communicated withineach facility.
There should be sufficient indication-specific CT protocols available and maintained toprovide an efficient and comprehensive optimisation imaging process.
The process of protocol optimisation should involve evaluation of clinical image quality
and technical measurements of image quality in phantoms as a part of regular QA.
Analysis of dose performance in scans of phantoms performed in parallel can be useful,
together with measurements of noise, limiting resolution and contrast visualisation.
Changes to protocols should be made in stages, checks made to confirm that the desiredchanges have been achieved and a dose audit performed at an early stage.
Protocol development should be a continuing process with measurements being made of
the impact of changes and the whole process repeated.
Radiologists, radiographers and medical physicists should all feed into protocol
development; other stakeholders (clinicians and vendor application specialists) may also
add information to the local optimisation process.

2387

80

DRAFT REPORT FOR CONSULTATION: DO NOT REFERENCE

2388

Box 4.6. Optimisation arrangements at different levels of development.
In ICRP (2022) and in the introductory section of this document the range in resources andexpertise that are available in different facilities is discussed. This presents significant
challenges in setting out steps in optimisation that are appropriate for each facility. In order toprovide assistance to users in the development of optimisation strategies for their department,
the arrangements that should be in place for facilities at different stages of development arelisted below for C: Basic; B: Intermediate; and A: Advanced levels. Facility staff andmanagers should use these lists as a guide to reflect on the arrangements that are already inplace and identify those that it would be appropriate to focus on for their next stage ofdevelopment. Facilities in Level D, still in the very early stages of developing optimisation
should consider arrangements within level C: Basic group that they need to put in place.
C: Basic Level
•
•
•
•
•
•
•
•
•
•
•
•

Requests for CT scans include reason for referral and clinical history of patient.
CT radiographers trained by vendor applications specialist.
Clinical protocols agreed for imaging of all key body regions
Separate paediatric protocols based on patient age (head) or body weight (trunk)Standard anatomical references used to set scan limits.
ATCM settings provide appropriate modulation for patients of all sizes.
Basic tube voltage selection based on indication, patient size and use of contrast
Reconstruction filters specified for common types of examination in use.
If available, IR implemented for selected procedures with adjustment of exposure factors,
after agreement with radiologists.
Acknowledgement of dose display and using DRLs (published or national) at least for themost general examinations (head, chest, abdomen).
Regular (daily tube wam-up and air calibration) constancy checks performed byradiographers (QC).
CT scanner QC tests to characterise scanner performance carried out regularly, at least
annually.

B: Intermediate Level
•
•
•
•
•
•
•

Comprehensive scan protocols available for a wide range of clinical indications
encountered regularly and agreed by all radiologists.
Protocols agreed for scanners throughout facility based on similar criteria.
Consistent nomenclature and naming of indication-based protocols throughout facility.
System in place for regular review of protocols by core team.
Protocols include adjustment in tube potential according to patient size (with or without
contrast), and appropriate mAs values chosen based on CNR evaluation.
Protocols optimised through careful choice of exposure factors.
Utilisation of specific scanner features for improved optimisation and patient safety.

81

DRAFT REPORT FOR CONSULTATION: DO NOT REFERENCE

Box 4.6. (Continued)
B: Intermediate Level (Continued)• ATCM settings specified based on patients’ clinical conditions and sizes.
• ATCM and ATVS set up based on image quality references agreed with radiologists basedon review of clinical images.
• Minimal use of multiple pass scanning through same body part, unless necessary forspecific clinical indications.
• Iterative or deep learning reconstruction used for the majority of examinations with
reduction in exposure derived from evaluation of the quality of resulting images.
• Regular monitoring of doses and comparison of the doses with the DRLs
A: Advanced Level
•
•
•
•
•

•
•
•

•

•
•

Use of advanced technology and software for optimisation including IR or deep learning
reconstruction, dual energy CT and, most recently, photon counting CT.
Unified guidelines for indication-specific scan protocols throughout organisation.
Separate paediatric protocols based on clinical indications and patient age (head) or bodyweight/thickness (trunk)Consistent nomenclature and naming of indication-based protocols throughout
organisation.
Agreed system in place for revision of protocols, possibly with the lead-radiologist foreach organ/body part being the person-in-charge and collaborating with the otherradiologists, radiographers and medical physicists involved.
Harmonised scan parameter settings for all CT scanners of similar type and uniformity of
performance between different scanners in multi-scanner and multi-site organisations.
Process in place for continual review and assessment of protocols taking account offeedback on clinical image quality and dose survey results.
Utilisation of organisation wide dose and protocol management systems in order toprovide continual data for monitoring and improvements; evaluation of safety events, andnear misses.
Utilisation of anthropomorphic phantoms and/or simulation models to perform more
extensive dose and image quality evaluations on scanner protocols for optimisation andresearch.
Utilisation of model observers and other methods for clinically relevant image quality
assessments.
Communication with radiological community to share best practices (up to date protocols)
and with the public to communicate benefit/risk information.

2389

82

DRAFT REPORT FOR CONSULTATION: DO NOT REFERENCE

5. PAEDIATRIC PROCEDURES

2390
2391

(238) Key messages in this section:

2392
2393
2394

•

Paediatric protocol optimisation requires an understanding of the clinical indication,
patient size, the ability of the patient to cooperate, and alternative examinations
available locally to answer the clinical question.

2395
2396
2397

•

The radiological professionals (the core team of radiographers, radiologists, andmedical physicists) must have adequate education and training in optimisation ofimaging for infants and children.

2398
2399
2400
2401

•

Adopting a graded approach, the next step is education of the referring clinicians
and patients/families, followed by the managers, regulatory agencies, and otherstakeholder groups to enable an integrated system in which understanding of thecomplex processes involved is continuously improved.

2402
2403
2404
2405

•

Referrers, children, their parents, and carers should be involved in shared decisionmaking throughout the process of considering, performing, and reviewing imaging
examinations. Education through web and written literature improves both
radiological protection and health literacy.

2406
2407
2408

•

Monitor collimation as part of the QA programme in digital radiography to ensurethat radiographers collimate radiographic exposures properly, rather than cropping
images after the exposure.

2409
2410

•

A grid is usually unnecessary for radiography or fluoroscopy of infants and children
under the age of 4 y, and may not be required for chest imaging of older children.

2411
2412
2413
2414
2415

•

Patient age is a poor substitute for thickness in determining exposure requirements.
As with any projection radiograph, body part thickness is the most important
determinant for the technique. The abdomens of the largest 3-year-olds are the same
size as the abdomens of the smallest 18-year-old. Use of weight is a better alternative
to age that can be measured relatively easily.

2416
2417
2418

•

Use dose reduction methods when practicable with fluoroscopy, including virtual
collimation, removal of the grid, additional copper filtration, last image hold, andpulsed fluoroscopy on the lowest possible setting.

2419
2420
2421

•

The optimisation core team (radiographer, medical physicist and radiologist), shouldshare bi-directional learning with clinicians, families, and other stakeholders. They
should review imaging protocols periodically to implement best practices.

2422

5.1. Requirements for imaging paediatric patients

2423
2424
2425
2426
2427
2428
2429
2430

(239) This section will consider improvements in radiological protection and safe andeffective imaging care of infants and children. There are specific requirements relating to
optimisation of imaging for paediatric patients, and optimisation strategies (the process of
selection of imaging protocols) to be followed when imaging these patients. An important
approach to improving the radiological protection and the imaging outcomes of children is byraising awareness of issues through education and inclusion of all stakeholders: the patient(when appropriate), parents, carers, radiographers, paediatric clinicians, medical physicists,
and nurses in this process (Fig. 5.1).
83

DRAFT REPORT FOR CONSULTATION: DO NOT REFERENCE

2431
2432
2433
2434

Fig. 5.1. An example of an expanded inclusiveness in optimisation education to all
stakeholders. The Image Gently layered approach to RP for children: rethinking the approachto optimisation. (with permission from Image Gently).

2435
2436
2437
2438
2439
2440
2441
2442
2443
2444
2445
2446

(240) Less than 10% of healthcare resources are spent on children so that much of the focus
and medical training is on adult care (Bui et al., 2017). This fact sometimes makes it difficult
to gain the attention of healthcare systems, health professionals, and the equipment
manufacturers to ensure that there is adequate education, training, and optimisation of imaging
for children, and most especially for infants (defined as age under one year). The default
policies, procedures, imaging protocols, and manufacturer equipment settings are all typicallyset for adults and these can—and do—lead to unnecessary irradiation, inappropriate or nondiagnostic imaging procedures, and to paediatric patient harm if there are false positives, false
negatives, or test complications. One size does not fit all for paediatric optimisation (Fig. 5.2).
Paediatric protocol optimisation requires an understanding of the clinical indication, patientsize, the ability of the patient to cooperate, and alternative examinations available locally toanswer the clinical question.

2447
2448
2449
2450

Fig. 5.2. An example of visual social media messaging from Image Gently. “The Message:
simple, direct, resonant, clear”. One size does not fit all for optimisation (with permission from
Image Gently).
84

DRAFT REPORT FOR CONSULTATION: DO NOT REFERENCE

2451
2452
2453
2454
2455
2456
2457
2458
2459
2460
2461

(241) The term optimisation requires a broader definition than has been applied in the past
(Fig.1.1) and a layered approach (Fig. 5.1) that begins with the medical physicist, radiologist,
and radiographer core team. The ICRP has provided guidance for diagnostic reference levels(DRLs) in ionising radiation imaging for children (ICRP, 2017) that is a starting point but not
an end point for improvement opportunities (ICRP, 2022). For example, setting of a DRL
should be followed by reaudit and continual reassessment to determine whether the facility canachieve the median reference value. The core imaging team should engage in ongoinginteraction with all stakeholders involved in the imaging processes, with continuous learning
to improve optimisation and outcomes. These interactions and outcomes include the patients,
the workers, and the families and carers who often hold the children for the imaging to be
successful.

2462

5.1.1. Why “children are not small adults”

2463
2464
2465
2466
2467
2468
2469
2470
2471
2472
2473
2474
2475
2476
2477
2478
2479
2480
2481
2482
2483
2484
2485
2486
2487
2488
2489
2490
2491
2492
2493
2494
2495
2496
2497

(242) On average, infants and children have a higher radiation sensitivity compared to adults.
Many of their organs are more sensitive to radiation than those in adults, while other tissues
have similar radiosensitivities (UNSCEAR, 2013). Moreover, the longer life expectancy inchildren allows more time for any harmful effects of radiation to manifest and provides anotherrationale for special consideration for imaging children.
(243) It is important to understand the unique considerations and approaches when imaging
children for setting the scene, before moving to the specific requirements relating to
optimisation of imaging for paediatric patients. If the saying is old and well-trodden that‘children are not small adults’, there is a good reason for saying it again. It is easy to see thatpatient size varies in the paediatric world much more than in the adult one, and by a factor of
100; yet not that long ago, there were no differences in CT protocols for children and adults
except at specialised childrens’ hospitals (Donnelly et al., 2001). These ‘one size fits all’ CT
protocols used by community hospital imaging facilities were one component that resulted in
unnecessary radiation doses to children.
(244) Yet, there are other reasons that children require more attention before, during, and after
their imaging care (www.imagegently.org). One important consideration is an understandingof paediatric medicine that requires proper selection of the imaging for an infant/child who
may not cooperate or who it was not possible to sedate. The pathology in children is different
from that of adults so that the clinical protocols differ in basic ways; when children havecancers, these are large sarcomas that grow quickly, not carcinomas as seen in adults, and thisenables CT protocols that have lower mAs values to be used, and in addition the radiologist
interpreters may tolerate more image noise. Further, children have congenital anomalies andinfections more often than adults. When recurrent imaging of the same body part is required,planned use of fewer images, more collimated radiographs and fluoroscopy, or CT with noisier
images, that can be acquired with lower radiation doses should be considered. When imaging
is requested, other considerations must include whether sedation or anaesthesia will be neededin the infant or younger child. If the smaller child can undergo imaging (e.g., ultrasound)
without sedation, it is safer, less costly, and sometimes faster for all. Medical and radiologicalprofessionals must have adequate initial education and continued commitment to training inradiological protection to care for infants and children (Vassileva et al., 2022). Surveys bynational and regional radiography organisations indicate inadequate paediatric training andwide variations in digital paediatric radiological practices (Morrison et al., 2011; McFadden etal., 2018; Alsleem et al., 2019; Foster et al., 2019).
(245) The radiological professionals (the core team of radiographers, radiologists, andmedical physicists) must have adequate education and training in optimisation of imaging for85

DRAFT REPORT FOR CONSULTATION: DO NOT REFERENCE

2498
2499
2500
2501
2502
2503
2504
2505
2506
2507
2508
2509
2510
2511
2512
2513

infants and children. Then, adopting a graded approach, the next step is education of thereferring clinicians and patients/families, followed by the managers, regulatory agencies, andother stakeholder groups to enable an integrated system in which understanding of the complex
processes involved is continuously improved. In order to be successful, the imaging facility
must gain the trust of the child and the parents or carers, as a child will not cooperate unlesshe/she feels safe. Therefore, the use of distractors (toys) and a nurse or childcare specialist to
calm the child and family while undertaking the imaging procedure can make all the difference
between success and failure.
(246) A culture of safety and of radiological protection is often present in paediatrichealthcare facilities (Malik et al., 2020). To obtain this level of awareness, radiology workers
require education and training in how to work with children and families. When working in a
medical imaging facility, the ICRP has recommended minimum levels of radiologicalprotection education and ongoing training for all types of workers (ICRP, 2009). When working
with infants and children and their families, further education, awareness, and ongoing training
may be helpful. The following sections focus on several clinical, medical physics, and practicalconsiderations that are known to improve paediatric imaging outcomes.

2514

5.1.2. Preparing the child and family

2515
2516
2517
2518
2519
2520
2521
2522
2523
2524
2525
2526
2527
2528
2529
2530
2531
2532
2533
2534
2535
2536
2537
2538
2539
2540
2541
2542
2543
2544

(247) There is no more overlooked quality factor in paediatric radiology than to have anexperienced and patient radiographer when preparing the child and family or caregiver.
Inadequate or unsuccessful imaging occurs in facilities that do not image children regularly or
do not invest in training staff to learn to care for children. The facility should provide a childfriendly environment that includes warm colours, decorations, furniture for children, with toys
and distractions in the imaging rooms, and the provision of a childcare specialist if possible(Image Gently). These specialists may use a mock imaging room to introduce the child andfamily to equipment and a procedure beforehand (www.radiologyinfo.org). Online resources
for the requesting clinician, the radiologist, and the patient and family about preparing thepatient are available in English and Spanish on international (WHO, 2016; ACR-RSNA, 2020;
ESR, 2020; IAEA, 2020) and regional RP campaign websites. Some provide podcasts
describing what to expect from their imaging procedures from a child’s viewpoint.
(248) When children are imaged, parents have long pushed for a culture of safety andtransparency—ensuring that the child and their family are an integral part of the care team.
This has become a concept called shared-decision making that is a key component of patientcentred healthcare. It is a process in which physicians and patients work together to makedecisions and select imaging tests, treatments and care plans based on clinical evidence thatbalances risks and expected outcomes with patient preferences and values (HealthIT, 2013).
Referrers, children, their parents, and carers should be involved in shared decision-making
throughout the process of considering, performing, and reviewing imaging examinations.
Education through web and written literature improves both radiological protection and healthliteracy.
(249) Parents, families, and health professionals have worked together over time to provide
imaging facilities that are safe and have a welcoming environment for children. For example,
the workers use language that is easily understood and invites the patient/family to participate,
and they use the patient/parents’ language (via a translator). A recent study in the emergency
setting revealed that less CT and radiographic imaging is undertaken if a translator is provided.
In addition, all imaging professionals should be prepared to answer the child’s or parents’questions—or to direct them to an appropriate colleague to respond to concerns raised. A parent
or carer is often present in the imaging room to hold the child so that they remain still during
86DRAFT REPORT FOR CONSULTATION: DO NOT REFERENCE

2545
2546
2547
2548
2549
2550
2551
2552
2553
2554
2555
2556
2557

imaging and to comfort them. This decreases anxiety and the chance that repeat radiation
exposures will occur.
(250) Many imaging facilities have developed written decision aids or direct parents to web
sites that provide information that helps them understand why their child is undergoing an
imaging procedure, how to prepare for it, and what to ask about, as well as a description of
possible benefits and risks, alternatives to the procedure, and the next steps for the patient andfamily (ICRPaedia; Image Gently; ACR-RSNA, 2020). In order to put risks into context anapproximate value for the effective dose from a chest x-ray on a child is 0.1 mSv, equivalent
to about 10 days exposure to natural background radiation (Image Gently, 2022a).
(251) To prevent unnecessary radiation exposures and repeat procedures, a time investment,on the one hand educating the referring physicians and on the other explaining to the child andfamily about the imaging procedures, are crucial. Additionally in the long run, such actions
save a significant amount of anxiety, stress, and tears on the part of all involved in the process.

2558

5.1.3. The Adolescent and Pregnancy Status

2559
2560
2561
2562
2563
2564
2565
2566
2567
2568
2569
2570
2571
2572

(252) An assessment is required for female adolescents (age 12–18 years) of the possibilityof pregnancy prior to a procedure involving exposure of the abdomen. This group is particularly
vulnerable to social and parental pressures that can potentially result in the patient providing
misinformation about her reproductive status. The imaging facility’s standard adult policy for
documentation of the last menstrual period date and verbal and/or written screening for
pregnancy status may therefore not be sufficient for this group. Staff may question adolescents
separately from their parents and many facilities require a pregnancy test if there is any doubt
about possible pregnancy, while in some countries imaging facilities may have policies that
require all female adolescent patients to undergo urine pregnancy testing, unless they are
known to be pregnant. The imaging procedures for which precautions are required include:
Abdominal-pelvic CT; and angiography and interventions in the pelvic area under fluoroscopy.
Additional procedures to consider include radiography of the abdomen, pelvis, hips, andlumbosacral spine (see for examples ACR-SPR, 2018).

2573

5.1.4. Patient positioning and immobilisation

2574
2575
2576
2577
2578
2579
2580
2581
2582
2583
2584
2585
2586
2587
2588
2589

(253) Proper patient positioning is key to a successful imaging procedure and often
overlooked when the infant or child is not cooperative. In these circumstances, measures should
be taken to ensure the patient is immobilised during imaging. An immobilisation device may
be used or a parent/worker can hold the patient to prevent them from moving. This will allow
the beam to be centred correctly with the proper projection and collimation needed. In the past
any shielding would be placed at this time, but this is no longer considered appropriate (Section
2.3.4) and more efficient optimisation methods should be implemented.
(254) Immobilisation is required for many children when performing radiographic studies.
Devices that are approved by the local facility, such as sponges, plexiglass, or sandbags may
be used in infants or for small body parts (fingers, hands, wrists, toes). Immobilisation devices
for supine or upright chest and supine abdominal radiographs are available for infants. Whenthe child needs to be held during a radiographic exposure, the parent or carer would usually be
asked to do this unless they are pregnant. No part of the body of the parent/carer should be in
the radiation field of the exposed radiographs, fluoroscopy, or CT exams; a QA process forprocedures may be helpful for peer education. Radiographers and other facility workers (nurses)
may also help to immobilise a child; however, this would be regarded as an occupational
87

DRAFT REPORT FOR CONSULTATION: DO NOT REFERENCE

2590
2591
2592
2593
2594
2595

exposure and care should be taken to ensure that no individual is exposed to scatter radiation
repeatedly. Lead personal protective equipment should be provided for staff and carers who
provide assistance. Portable radiography in particular should have a QA programme forattention to positioning, collimation, artefacts, and variation in dose parameters for repeatedchest and abdominal radiography in the Neonatal Intensive Care Unit (NICU). For moreeducational materials see Image Gently (2020e).

2596

5.1.5. The importance of collimation in children

2597
2598
2599
2600
2601
2602
2603
2604
2605
2606
2607
2608
2609
2610
2611
2612
2613
2614
2615
2616
2617

(255) Collimation matters more in limiting unnecessary radiation dose to infants and children
than in adults. Collimation should be performed prior to radiation exposures. If a radiographer
does not collimate a chest radiograph in a neonate (age< one month) properly, it is likely toinclude radiosensitive organs both above (thyroid, red marrow in the skull, lens of the eye) andbelow (stomach, colon) the area imaged. When a fluoroscopy operator performs an upper gastrointestinal procedure on a neonate and does not use adequate collimation, they will give
unnecessary exposure to radiosensitive breast tissue above the region imaged, and the pelvis
and ovaries below. When an abdominal helical CT scan is performed on a child, more than therequired body part may be irradiated because of overranging (Section 4.2.2), which may expose
the female breast and more of the pelvis. Portable radiography should have a QA programme
to monitor collimation which can be a particular issue (Fig 2.3).
(256) Collimation should be monitored as part of the QA programme in the digitalradiography environment to ensure that radiographers collimate radiographic exposuresproperly, rather than cropping images after the exposure. (Section 2.3.2). A survey by theAmerican Society of Radiologic technologists showed that 50% of radiographers used
postprocessing to collimate their radiographs in 75% of their cases (Morrison et al., 2011) andthis practice continues in many facilities. The use of electronic collimation after exposure
during postprocessing increases doses to patients and may not be evident in the PACS or the
medical record. The need to collimate must be stressed during radiographer training.
Assessment of competency and periodic review training using a doll or a phantom may be
helpful.

2618

5.2. Adjustments in image quality requirements and dose with patient size

2619
2620
2621
2622
2623
2624
2625
2626
2627
2628
2629
2630
2631
2632
2633

(257) The acceptable level of image noise for answering a clinical question is often higher for
paediatric imaging in facilities where images are interpreted by trained paediatric radiologists,
as compared to adult imaging. The clinical indications in children differ greatly from adults,
and depend on the age, time of year (infection prevalence), and regional genetic andenvironmental factors. However, there are trade-offs in image quality and dose with smaller
body parts and/or thinner CT acquisitions, in that the image noise will increase. Good
radiographic, fluoroscopic, and CT technique includes attention to patient positioning, fieldsize and collimation; optimisation of exposure factors; use of pulsed fluoroscopy, limiting
fluoroscopy time, and consideration of whether a grid should be used.
(258) Use of a grid in radiography or fluoroscopy is usually unnecessary for infants andchildren under the age of 4 years (or <12 cm in AP diameter). In addition, parts of the body >12cm with structure containing air (such as the chest) can be imaged without a grid. In these cases,
there is a trade-off between image quality and dose, as a higher mA and longer exposure time
are required if a grid is used. When high image resolution is necessary in interventional
procedures, the use of copper filtration with a grid is useful. Grids should be modified
88

DRAFT REPORT FOR CONSULTATION: DO NOT REFERENCE

2634
2635
2636
2637
2638
2639
2640
2641
2642
2643
2644
2645
2646
2647
2648

depending on patient size (2:1 to 6:1 for small size to at least 10:1 for chest radiographs andpreferably 12:1) and for 100-130 cm source image distance SID (Image Gently, 2022a).
(259) The use of pulsed fluoroscopy, at the lowest rate tolerated by the operators at the facility,
reduces the radiation dose significantly below the continuous fluoroscopy setting (Box 3.2).
Experienced practitioners use 7.5 or lower frames per second for routine general fluoroscopy,
but interventional cases require faster rates for cine acquisition mode; higher frame rates areoften used for video modified barium swallow studies.
(260) The default setting for imaging equipment set by vendors is for adult imaging and must
be reset for infants and children. Key provisions include the techniques mentioned above as
well as the development of paediatric specific protocols for common clinical conditions (seefor example a sample technique chart for paediatric abdominal radiography, slide 53 of 66,
Keith Strauss, (Image Gently, 2022a)). There is a need for more standardised, specific CT
paediatric protocols to be developed, that can be made available to all centres undertaking
paediatric exposures for common conditions, with 5–7 weight categories for body CT imaging
and 2-3 for head CT (ICRP, 2017; IAEA, 2020; AAPM, 2022).

2649

5.2.1. Radiography

2650

5.2.1.1. Choice of exposure factors and exposure levels

2651
2652
2653
2654
2655
2656
2657
2658
2659
2660
2661
2662
2663
2664
2665
2666
2667
2668
2669
2670
2671
2672
2673
2674
2675
2676
2677
2678
2679

(261) In large surveys, 74–85% of all ionising radiation imaging procedures in children areradiographs (UNSCEAR 2000, 2008; Dorfman et al., 2011; NCRP, 2019). Digital radiographs
use postprocessing to adjust for over and under exposures with 43% of paediatric radiographs
being overexposed (Don, 2004). Some modern equipment provides icons for small, medium,and large patient sizes, but the paediatric sizes may not be included. It is vital to ensure that
exposure settings used are not higher than necessary. The Image Gently Campaign ‘Back to
Basics’ approach can be used as a mnemonic to evaluate image quality. First, there are ten steps
to understanding and applying the basics of the digital imaging environment in paediatrics.
(262) Understand the basics of digital imaging. Digital radiography has several advantages
over traditional screen film radiography (see Section 2). It has a latitude of exposure that is
approximately 100 times greater, reducing the number of repeat examinations due tounderexposure and overexposure. Image manipulation (processing) is possible to change theappearance of the image thereby making subtle characteristics in the image more apparent. The
electronic images can be stored and distributed anywhere within a healthcare system, providing
access to the images within minutes after exposure. While the spatial resolution (sharpness) of
the digital image is less than an image on film, the superior contrast and other improvements
in image quality, including image processing available only in the digital image, result insuperior clinical studies with digital radiography.
(263) Understand the challenges associated with digital imaging: DR is fundamentallydifferent from film-screen, and exposure creep can lead to overexposures (see Section 2.2.3)(Gibson and Davidson, 2012). Moreover, vendor dependent image acquisition and terminology
variation in processes has led to confusion in understanding image quality and techniques.
Inadequate initial education and ongoing training in the radiology community about theseissues in using DR have exacerbated problems with its use in children.
(264) Learn exposure terminology standards. Target Exposure Index (EIT), Exposure
Index (EI), and Deviation Index (DI) are discussed in Section 2.2.3. The DI indicates by how
much the exposure for an imaging study deviates from the target value (see Table 2.2).
Understand and pay attention to the kerma-area product (KAP) readings.
(265) Establish manual technique charts using a team approach. The team includes the89

DRAFT REPORT FOR CONSULTATION: DO NOT REFERENCE

2680
2681
2682
2683
2684
2685
2686
2687
2688
2689
2690
2691
2692
2693
2694
2695
2696
2697
2698
2699
2700
2701
2702
2703
2704
2705
2706
2707
2708
2709
2710
2711
2712
2713
2714
2715
2716
2717
2718
2719
2720
2721
2722
2723
2724
2725
2726
2727
2728

radiographer, radiologist, medical physicist, and vendor. This may be particularly important for
infants and small children. The automatic exposure control (AEC) sensors commonly used in
adults, are often problematic in children if the body part is smaller than the set of AEC sensors(Goske et al., 2011). In some cases, the AEC may be used on children if only the central sensor
is activated and the child’s body part is positioned to completely cover the entire single sensor.
However, for infants and smaller children the imaged area of anatomy may be smaller than the
single sensor and then manual techniques may be more appropriate. Focused exposure charts
are important for key common exams such as chest, abdomen, and small parts.
(266) Measure body part thickness. X-ray absorption/transmission depends on thecomposition of the body part being imaged and the body part thickness is the most important
determinant for the technique. Patient age is a poor substitute for thickness, as the abdomensof the largest 3-year-olds may be similar sizes to those of the smallest 18-year-old (Kleinman
et al., 2010). Therefore, patient age cannot reliably be used as a guide for techniques. Reverting“Back to Basics” by measuring patients with callipers will ensure that a standardised technique
is selected. Knowing the body part and its thickness, one can then set the tube potential,
filtration, and mAs for that specific study to “appropriately size” the examination for the child.
Automated evaluation of patient thickness based on the exposure factors used and a knowledgeof the characteristics of the x-ray detector might also be an option (Worrall et al., 2020). The
goal is for reproducible, consistent images for children with body parts of similar sizes.
(267) Use grids only when body thickness is >10–12cm. The main purpose of anti-scatter
grids is to remove scatter from the image to improve the subject contrast in the image. Scatterstarts to significantly degrade subject contrast in the image when the body part is over 10–12
cm of water-equivalent thickness. Structures that are greater than 12 cm thickness containing
air, especially chest radiographs, can be successfully imaged without a grid. The use of grids
should be minimised in children with less than 12–14 cm thickness (Carlton and Adler, 2013).
Depending on the grid selected, anti-scatter grids double or triple the exposure factors
necessary to obtain an adequate image.
(268) Collimate prior to the exposure. With the advent of digital radiography, it is possible
to open the collimators, then manipulate and electronically crop the image after the exposure.
Radiologists may not be aware that cropping is widely used (see Section 2.3.2), yet radiologists
are responsible for the image before cropping occurs. The cropped portions of the body are
exposed to unnecessary radiation. While opening the collimators may be necessary
occasionally for inclusion of anatomy such as an arm in a percutaneously inserted central
venous catheter, under most circumstances it is better to immobilise the patient and collimate
appropriately before the exposure rather than crop the image later.
(269) The benefits of collimation prior to exposure are reduction in the area exposed,
lowering the patient dose and KAP, and minimising scattered radiation, and so improving
image quality (Curry et al., 1990). In addition, a well-collimated field will exclude extraneous
structures outside the area of interest, such as shields that might affect the applied image
processing. Wide open collimators may affect the EI, giving a false indication of the exposure.
(270) Additional filtration: In the paediatric patient, total radiation must be kept low. Thisis the case with digital radiography or when high speed radiography systems are used. Not all
generators (particularly mobile radiography units) are capable of delivering the short exposure
times that are required for these higher tube potential techniques. Consequently, lower tube
voltages are often used for paediatric patients and these result in higher patient doses. The
insertion of additional filtration will reduce the incident air kerma rate and allow delivery oflower doses with higher tube voltages within the range of exposure times available on such
equipment. The benefit of copper filtration is discussed in Box 2.3 and Section 2.2.2.
(271) Rare-earth filter materials with absorption edges at specific wavelengths have little or90

DRAFT REPORT FOR CONSULTATION: DO NOT REFERENCE

2729
2730
2731
2732
2733
2734
2735
2736
2737
2738
2739
2740
2741
2742
2743
2744
2745
2746
2747
2748
2749
2750
2751
2752
2753
2754
2755
2756
2757
2758
2759
2760
2761
2762

no advantage over simple inexpensive aluminium-copper filters. All tubes used for paediatricpatients in stationary, mobile, or fluoroscopic equipment should have the facility for adding
additional filtration, and for changing it easily when appropriate. Usually up to 1 mmaluminium plus 0.1 or 0.2 mm copper as additional filtration is adequate. For standard
radiographic voltages, each 0.1 mm of copper reduces output by about the same as 3 mm ofaluminium, but removes a higher proportion of the photons between 20 and 40 keV (ICRP,
2013b).
(272) Display technique factors for each image. The radiologist and radiographer should
become familiar with technique factors used for common paediatric examinations. Thisrequires that the tube potential, mAs, added beam filtration, EI, DI, and ideally KAP values bepresent on the displayed image (Willis and Slovis, 2004). The image processing organ
programme (e.g. portable chest, abdomen, hand) should also be displayed. These data provide
feedback to the radiologist and can help in solving problems when an image is not acceptable.
(273) Accept the noise level appropriate to the clinical question. Radiologists preferimages that have little noise (Don, 2004; ACR–AAPM–SIIM–SPR, 2017), but noise
intolerance can lead to exposure creep. To avoid this, radiologists need to become familiar
with the EI values for their equipment and understand the relationship between exposure
indicators and the visual appearance of noise in an image (Section 2.2.3). Exposure creep can
be avoided through routine QA monitoring of the DI and the level of image noise.
(274) Experienced paediatric radiologists may be tolerant of more noise in some body tissues
than in others. For example, noise does not affect the visualisation of high-resolution structures,such as bone detail, or the endotracheal tube or chest tube (Don, 2004). While the ability toidentify disease processes, such as surfactant deficiency disease/respiratory distress syndromeof the premature newborn and low contrast structures, is more noise sensitive (Roehrig et al.,1997). As users become more comfortable with the technique/noise relationship with digitalradiography, lower-dose follow-up studies that are tailored to answer a specific question, suchas checks on positioning after adjusting line placement, may become more common.
(275) It is critical that radiologists, radiographers, and medical physicists (the core team)develop standards for their imaging facility through the QA programme (ICRP, 2022). An
important element of this is recording and monitoring exposure indicators (Section 2.2.3,
Table 2.2). In addition, regional and national DRLs are being developed for common imaging
procedures, although provision of paediatric ones lag behind those for adults. The EU publishedPiDRLS in 2018 that includes paediatric abdomen, chest, skull, and pelvis radiography DRLs
at several age or weight categories (ICRP, 2017; EU, 2018 Table 10.2a).

2763

5.2.1.2. The Image Gently Back to Basics Tool for Evaluation of Image Quality

2764
2765
2766
2767
2768
2769
2770
2771
2772
2773
2774
2775

(276) The Word ‘BASICS’ is a mnemonic tool to help operators to remember aspects thatmust be considered when taking a radiograph; Beam, Artefacts, Shielding, Immobilisation andIndicators, Collimation, and Structures.
• Beam: is the anatomy centred in the beam? Is the tube angled correctly?
• Artefacts: are there any external artefacts that are obstructing the beam?
• Shielding: Gonadal shielding is no longer considered appropriate for routine x-ray imaging
as protection it provides from scatter is minimal (see Section 2.3.4; AAPM, 2019c; Hiles
2020, 2021). If the family requests shielding because it was used previously, the facility
may use it with the family sharing in the decision making. When appropriate the last
menstrual period should be documented to assess for pregnancy (see Section 5.1.3).
• Immobilisation: Could immobilisation help to reduce the chance of a repeat exposure?
Should the facility seek immobilisation advice and training from a paediatric imaging
91

DRAFT REPORT FOR CONSULTATION: DO NOT REFERENCE

2776
2777
2778
2779
2780
2781
2782

•
•
•

facility?
Indicators: What does the EI mean and how can adjustments be made for similar patients
undergoing the same exam? Is the DI appropriate? (see Section 2.2.3 and Table 2.2)
Collimation: Only expose the patient to the necessary amount of radiation. Never leave
collimators open and rely on post-exposure, electronic collimation, as this will give thepatient additional exposure.
Structures: Check if the necessary anatomy or device is properly demonstrated.

2783

5.2.1.3. Imaging of neonates (up to 1 month) and infants (up to 1 year)

2784
2785
2786
2787
2788
2789
2790
2791
2792
2793
2794
2795
2796
2797
2798
2799
2800

(277) In general, a small focal spot can be used in imaging the trunk for neonates and infants
whereas a larger one is used for children and adults. A nominal focal spot value between 0.6
and 1.3 mm is usually suitable for paediatric patients. When a bifocal tube is used forradiography, the nominal focal spot value should be used, allowing for the most appropriate
setting of exposure time and tube voltage at the chosen SID. This may not always be the smaller
one (ICRP, 2013b).
(278) When infants need radiography, this may be performed with portable radiographic units
and immobilisation may be necessary. The Back to Basics steps for image optimisation areimportant (Section 5.2.1.2). Manual technique charts are often required for optimisation.
(279) Consider how an AP chest radiograph of a neonate, AP thickness 6 cm, compares to
one of a large adult with a PA thickness of 30 cm. The half-value layer (HVL) of soft tissue(the amount of tissue that will decrease the air kerma by half) is approximately 3 cm at 70 kV
for imaging equipment with standard filtration. The difference in thickness of eight HVLs
requires a reduction in mAs by a factor of 256. Thus a typical neonatal (portable) chest x-ray
with a DR detector might be performed with <60 kV and approximately 1 mAs.
(280) The Image Gently Campaign has a safety checklist for radiographers performing
portable radiographs on children that can also be used for adults (see Box 2.4).

2801

5.2.2. Fluoroscopic imaging

2802
2803
2804
2805
2806
2807
2808
2809
2810
2811
2812
2813
2814
2815
2816
2817
2818
2819
2820

(281) While the use of fluoroscopy in adults has markedly decreased over the past decadeswith the increase in cross-sectional imaging and other endoscopic procedures, generalgastrointestinal and genitourinary fluoroscopy continue to be routinely performed and valued
in infants and children. The general operation and approach to optimisation is considered indetail in Section 3, but it is critical to understand the justification and optimisation of common
procedures in the paediatric community. When considering the use of fluoroscopy in a child,in addition to optimisation of technique, a further question is whether alternative imaging
procedures such as ultrasound could be used.
(282) Careful selection of equipment that provides safe and quality imaging for children isimportant. In the clinical practice of paediatric fluoroscopy, far fewer x-rays should be needed
to create the images required for diagnosis compared to adult fluoroscopy, providing
opportunities for reducing doses in infants and smaller children. Whereas the ESAK rate for an
abdominal exam on a large teenage patient may be 90 mGy min-1, that for a neonate may be
only 1 mGy min-1 in a properly configured machine. The equipment should have the capability
to facilitate dose reduction strategies. Effective doses from a fluoroscopic examination on achild that might be 0.45–0.59 mSv with continuous mode fluoroscopy might be only 0.05–0.07
mSv if the procedure were fully optimised (Image Gently, 2022b), so there is a need for
operators to understand and use all the facilities available.
(283) While barium or iodinated contrast media are administered at room temperature in
92

DRAFT REPORT FOR CONSULTATION: DO NOT REFERENCE

2821
2822
2823
2824
2825
2826
2827
2828
2829
2830
2831
2832
2833
2834
2835
2836
2837
2838
2839
2840
2841
2842
2843
2844

adults, there is more use of contrast warmers for infants and young children. The use is not to
reduce the likelihood of vascular extravasation, but to avoid the risk of body temperature
decrease or even shock from contrast infusions into the gastrointestinal (GI) or genitourinary(GU) systems.
(284) A team approach to QA for dose management and image quality in paediatricfluoroscopy should be developed with the radiologist, radiographer, and medical physicist(ICRP, 2018a; Image Gently, 2020b). The development of paediatric DRLs will aid
optimisation. Few have as yet been established for fluoroscopy, but the European UnionPiDRLs include a DRL for micturating cystourethrogram (MCU) at 4 age levels (EU, 2018,
Table 10.2a). An example of self assessment in dose management and quality improvement for
MCU/VCUG paediatric fluoroscopy is available on the Society for Pediatrics Radiology website (SPR, 2008).
(285) Staff will be exposed to scattered radiation during fluoroscopy procedures, and theradiological protection principles of time, distance, and appropriate shielding should be applied(ICRP, 2018b). The scatter dose from patients should be lower in the paediatric environmentas patients are smaller, but more use of magnification may be needed, and require the operator
to move nearer to the patient to immobilise or position the patient properly.
(286) When performing fluoroscopy, a parent and/or carer may be welcomed into the room
to help calm the child and sometimes hold the child during the procedure. Care must be taken
to check that radiation dose management is performed for these individuals as well as for thepatient, the radiographer, and the operator. Is everyone properly shielded? Are the hands
holding the child out of the field of view? Is the patient positioned properly to start thefluoroscopy? The large relative size and noise of an image intensifier can be scary for young
children so that cooperation can be a challenge. Preparation and teamwork are key.

2845

5.2.2.1. Unique technical operator approaches

2846
2847
2848
2849
2850
2851
2852
2853
2854
2855
2856
2857
2858
2859

(287) There are a number of dose reduction methods to consider prior to commencement ofa fluoroscopic procedure on a child. These include the use of virtual collimation, lowattenuation table tops, removal of the grid, (the default setting is grid out where children are
imaged primarily), copper filtration in addition to aluminium, use of the last image hold option,
avoidance of magnification mode when possible, and the use of pulsed fluoroscopy on thelowest possible setting.
(288) Pulsed fluoroscopy settings should be the lowest possible that the operator is
comfortable using (3.5–7.5 pulses per second), depending on the procedure being performed.
The use of the last image hold feature allows not only time for the operator to review the image,to collimate or move the fluoroscopy image receptor, but it also allows the image to be stored.
If higher quality images are required for storage and review, the dose is increased by a factorof 10. However, these exposures may be justified to convince the clinician or surgeon of thediagnosis or to confirm a subtle abnormality or both. Optimisation is not always about lowering
the dose; it is about obtaining the image quality necessary to answer the clinical question(s).

2860

5.2.2.2. Suitable exposure factor programmes

2861
2862
2863
2864
2865

(289) Assuming that aluminium filtration is used, the minimum tube potential should be 65
kV for infants and range up to 100 kV for large children. The tube current usually ranges from
0.5 mA to 6 mA depending on the patient size (Image Gently, 2020b). When a 0.1–0.2 mm
thick copper filter is inserted in the beam, the tube potential for infants can be lowered to 55
kV. However, use of smaller thicknesses of copper may not alter the image quality and therefore,
93

DRAFT REPORT FOR CONSULTATION: DO NOT REFERENCE

2866
2867
2868
2869
2870
2871
2872
2873
2874
2875
2876
2877
2878
2879
2880
2881
2882
2883
2884
2885
2886
2887
2888
2889
2890
2891
2892

no change in the exposure factors is needed (Image Gently, 2020b).
(290) There is no difference between children and adults for the focus to image receptor
distance. During fluoroscopy, the patient should remain as far from the x-ray tube (at least 30cm) and as close to the flat panel detector or image intensifier as is comfortable to reduce dose.
High tube potential settings should be used to lower the dose.
(291) Patient dose should be recorded with all information made available from thefluoroscopic equipment (PKA, Ka,r, see Annex A and fluoroscopy time). Although fluoroscopy
time does not reflect the patient dose, it can be compared with that for other operators
performing similar procedures in the review of operator technique.
(292) Fluoroscopic patient entrance dose rates are normally limited to the region 80–100 mGy
min-1, 88 mGy min-1 (10 R min-1) in US and 100 mGy min-1 in Europe; however, when usingcine mode, this is not true. Therefore, for safety reasons, it is suggested that cine mode be
turned off when imaging infants and children unless required for interventional procedures.
(293) Anti-scatter Grids: Grids increase dose to the patient and may not be necessary forchildren with thicknesses less than 12 cm. When a grid is required, grid ratios of eight and line
numbers of 40 lines/cm (moving grid) are usually sufficient even at higher radiographic voltage.
(294) Automatic Dose Rate Control (ADRC): ADRC (or automatic brightness control)
should be switched off during fluoroscopic examinations where there are relatively large areas
with positive contrast medium (e.g. full bladders) to avoid excessive dose rates, (ICRP, 2013b).
(295) Use of equipment that provides small focal spots: For example, an x-ray tube withthree focal spots (0.3, 0.6, and 1 mm), typically found in neuroangiographic suites, provides
better high contrast resolution than the standard dual focal spot tube with a typical 0.5 mm
small focal spot.
(296) Use of copper filtration: While most modern fluoroscopic and radiographic equipmentused for paediatric examinations has added copper filtration, some units may not. Most tubes
in x-ray equipment have a minimum inherent filtration of 2.5 mm aluminium. Additional filters
can further reduce the unproductive radiation and thus patient dose (ICRP, 2013b).

2893

5.2.2.3. Portable fluoroscopy

2894
2895
2896
2897
2898
2899
2900
2901
2902
2903
2904
2905
2906
2907

(297) C-arm (portable) units for intra-operative use give higher doses to the patients and highscatter radiation to the operator; and are configured for adult patients. Mini C-arm units are
FDA approved for orthopaedic fluoroscopy; but are unfortunately sometimes used for otherapplications. There are paediatric-focused C-arm units that should be considered for use atchild-based facilities.
(298) When C-arm equipment is used, it is important to be aware of the proximity of the skinto the x-ray source in lateral and oblique views, as it may be closer than in the PA view andgive patients high skin doses. The source-to-skin-distance (SSD) should be maximised bymoving the table up away from the x-ray tube when the C-arm has been positioned. A separator
cone can be applied to ensure a minimum 30 cm separation between the patient and the tube.
Operators should be aware that oblique tube geometry means that the x-ray beam traverses a‘thicker’ section of the patient and will increase the fluoroscopic dose rate. When the C-arm is
put in the lateral position, the patient should be at a similar distance from the source to that
permitted for the PA view. Field overlap in different runs should be minimised (ICRP, 2013b).

2908

5.2.3. Fluoroscopically guided interventions (FGIs)

2909
2910

(299) The complexity of FGIs, especially in infants and young children, requires specifictraining in paediatric interventional procedures, and safety. Sedation or anaesthesia are required
94

DRAFT REPORT FOR CONSULTATION: DO NOT REFERENCE

2911
2912
2913
2914
2915
2916
2917
2918
2919
2920
2921
2922
2923
2924

for many procedures, and when contrast media and other medications are used, their volume
must be carefully monitored. Intravascular iodinated contrast and gadolinium are relatively
contraindicated in the neonate because of poor renal function, unless there is no alternative.
Major paediatric interventional procedures should only be performed by experienced paediatricinterventional radiologists due to their complexity.
(300) Optimisation and training for interventional procedures may include simulation with adoll or anthropomorphic phantoms and a pre-procedure checklist (Image Gently, 2020c).
Radiation dose reduction can be considered in terms of the fluoroscopic pulse rate. In general,
cardiac procedures use 30 pps where it is required to capture the rapid beat of the paediatricheart, while most other interventional procedures can use lower pulse rates to reduce the dose.
Pulse rates of 3.5 (minimum) or 7.5 pps are recommended in paediatric fluoroscopy whenpossible (ICRP, 2013b; Image Gently, 2020b). Further, multi-modality imaging in theinterventional imaging suite may allow use of ultrasound, especially in smaller children, and
2D tomography instead of CT.

2925

5.2.4. Multi-detector CT procedures

2926
2927
2928
2929
2930
2931
2932
2933
2934
2935
2936
2937
2938
2939
2940
2941
2942
2943
2944
2945
2946
2947
2948
2949
2950
2951
2952
2953
2954

(301) There are large variations in use of CT, and the techniques and dose levels delivered
across the world, which make optimisation important, especially for paediatric examinations(Smith-Bindman et al., 2019). Special attention to the principles of justification, optimisation,
and a team approach to a radiation dose management and image quality programme are
essential in paediatric medicine. Beyond the core team of radiographers, radiologists, andmedical physicists or engineer, the larger team extends to include the CT equipment
manufacturers (Fig. 5.1).
(302) Advances in CT technology have created new opportunities for clinical uses in children
with marked dose reduction and increased speed in image acquisition. These include iterativeand deep learning-based image reconstruction methods (Nagayama et al., 2021), photon
counting CT, and hybrid functional imaging capabilities (CT/PET, CT/SPECT). Sample
paediatric protocols of the head, chest, and abdomen with pelvis for each of the major vendors
and their commonly available CT models are available on the AAPM website (AAPM, 2022).
The European Union paediatric imaging project produced DRLs for head, chest, and abdomen
CT in four age groups for head CT and five weight categories for chest and abdominal CT (EU,
2018, Table 10.2b) and other evaluations of DRLs have since been published (Kanal et al.,2022).
(303) Dual energy CT (DECT) and spectral CT (Gottumukkala et al., 2019; Tabari et al.,2020) can enable lower patient doses to be achieved (Section 4.5.1). Protocols may be built
using less contrast media, ATCM, and iterative post processing to correct for barium and metal
artefacts. Other potential applications include imaging of children who have devices that
preclude the use of MRI; for vascular imaging; or use of virtual non-contrast body or neuroimaging to evaluate for stones or acute haemorrhage (Siegel and Ramirez-Giraldo, 2019; Tabar
et al., 2020) so that a single pass through a body part is sufficient.
(304) Adjustment of exposure parameters to suit the specific application, clinical need andinformation required should always be considered. An example where a low dose technique
was adequate is shown in Fig. 5.3. Keeping the dose low is important, but it is secondary totreatment of the patient, and sometimes there is a need to increase the mAs to identify particularfeatures and accomplish the clinical task (Fig. 5.4).

95

DRAFT REPORT FOR CONSULTATION: DO NOT REFERENCE

2955
2956
2957
2958
2959
2960
2961
2962
2963
2964
2965
2966
2967
2968

Fig. 5.3. Single image from a limited, low dose chest CT pre-surgery for Pectus Excavatum in
a 17-year-old boy. The dose is low, but would be less with newer equipment and a lower tube
potential. Technique: 120 kV, 12.5 mAs, rotation time 0.5 sec; dose indices CTDIvol 0.63 mGy,
DLP 11.2 mGy cm. The measured Haller Index was 3.6 (severe). (K. Applegate, Dept ofRadiology, University of Kentucky, retired)(305) There is scope for optimising CT and developing low and ultra-low dose CT protocols.
Some can be used on paediatric patients for specific indications such as pectus excavatum CT(Fig 5.3) and sinus CT pre-surgery. There is an Image Gently basic ten step guide to
optimisation for paediatric CT (Strauss K et al., 2010). A set of simple questions to ask andstatements to consider when planning a CT scan and developing a protocol are given in Box
5.1 (WHO, 2016, ICRP, 2017; ESR, 2020; IAEA 2020; Image Gently, 2020d) and important
aspects to consider for the successful imaging of children are listed in Box 5.2.
Box 5.1. Questions to ask and statements to consider when planning a CT scan of a child
•
•
•
•

•
•

Have you considered alternative imaging such as ultrasound or MRI?
If a CT procedure is selected, child size the dose by choosing the tube potential and tube
current appropriate for the size of the child (2-4 age categories are suggested for the headand 5-7 weight categories for the trunk) (ICRP, 2017).
The ‘scout’, ‘scanogram’, or ‘topogram’ is an AP or PA (and sometimes lateral) image
that is performed to select the start and stop points for the CT exam. The tube potential
and mAs can often be lowered from the pre-set values.
Use of contrast media: while iodinated contrast media are administered at room
temperature in adults with no increased risk of extravasation, there is more use of contrast
warmers in infants and young children to avoid the risk of temperature drop from contrast
infusions.
Scan only the indicated area of the body (do not over-range).
Only scan once through the body part; pre- and post-contrast phase scans and delayedscans rarely add information but do increase radiation dose (Rostad et al., 2018).

96

DRAFT REPORT FOR CONSULTATION: DO NOT REFERENCE

2969
2970
2971
2972
2973

Fig.5.4 Example of an immunocompromised child with leukaemia and possible
candidiasis. The protocol uses a mAs 20% higher than the standard to visualise a single low
density lesion in the liver (arrow). (K. Applegate, Dept of Radiology, University of
Kentucky, retired)Box 5.2. Important aspects to consider for the successful imaging of children include:
•
•
•
•
•
•
•
•
•
•

2974
2975
2976
2977
2978
2979
2980
2981
2982

Preparing the patient and family (as noted above for fluoroscopy)
Understanding why CT protocols differ from those for adults, it is not just about dose(see Section 5.1.2)
Choice of exposure parameters
Use of ATCM (automatic tube current modulation) with paediatric patients
Challenges in use of automatic tube voltage selection in children (non-intuitive need toincrease tube potential rather than decrease with some vendor software)
Post-processing with iterative reconstruction and/or other techniques
Dose audits of paediatric patients (ICRP, 2017, 2022)
Methods for dealing with differences in patient size in dose audit to obtain usable data (asize specific dose estimate, SSDE (Box 4.1) (AAPM, 2011a, 2014)
Use of software programmes that track dose and patient dose registries (Smith-Bindmann
et al., 2019; ACR-DIR 2022)
Reference to QA and dose management programme resources that are available for
guidance (Strauss et al., 2010; ICRP, 2017, 2022; ACR DIR, 2022; Image Gently, 2020d)(306) With the rapid acquisition time of CT imaging, it is uncommon to use sedation or
anaesthesia in children or infants. Therefore, it is recommended that short acquisition times areused whenever possible, after checking that the number or projections does not compromise
the quality of the clinical information. Exceptions include infants over 3 months (that cannot
be swaddled) to age 4 years and that require intravenous contrast media; also, those paediatricpatients who cannot be calmed through normal comforting by childcare specialists and/or
distractors (see Section 5.1.2). There are also very thin collimation procedures such as temporalbone head CT that may require sedation/anaesthesia. Simulation with phantoms may be usefulin making assessments.
97

DRAFT REPORT FOR CONSULTATION: DO NOT REFERENCE

2983
2984
2985
2986
2987
2988
2989

(307) Newer equipment includes safety features in terms of safety alerts to reduce protocol
errors although each facility must set levels and create their own protocols. The AAPM
‘Recommendations Regarding Notification and Alert Values for CT Scanners: Guidelines for
Use of the NEMA XR 25 CT Dose-Check Standard’ (AAPM, 2011b) includes a table forsuggested notification values. The CTDIvol alert level for the paediatric head age<2 years is 50
mGy and for age 2–5 years is 60 mGy; the notification value for the paediatric torso is 10 mGy
for age <10 years using the 32 cm CT phantom.

2990

5.3. Development of optimisation for paediatric imaging

2991
2992
2993
2994
2995
2996
2997
2998
2999
3000
3001
3002
3003
3004
3005
3006

(308) Optimisation of imaging for paediatric patients has additional challenges to those in
adult radiology, because of the range in size, tissue composition and radiosensitivity with age.
Digital imaging offers more flexibility in exposures, so that levels can be adapted to thediagnostic requirements for the needs of individual patients. However, in order for this to occur
staff need to be even more aware of dose levels and image quality requirements for diagnosis.
The optimisation core team (radiographer, medical physicist and radiologist), should share bidirectional learning with clinicians, families, and other stakeholders. They should review
imaging protocols periodically to implement best practices. Some of the arrangements thatmight be expected to be in place for x-ray facilities at different levels in the development of
optimisation are set out in Box 5.3 to assist in prioritisation of the introduction of arrangements
and processes.
(309) Open access internet sources can provide guidance on optimisation and radiologicalprotection relating to children. Many include paediatric imaging protocols, education andtraining for the radiology community, for referring physicians and staff, andfamily/carers.( ImageGently; ImageWisely; WHO, 2016; AAPM, 2022 (CT Protocols); IAEA,
2022; WFPI, 2022)

98

DRAFT REPORT FOR CONSULTATION: DO NOT REFERENCE

Box 5.3. Optimisation arrangements for paediatric radiology that should be in place forfacilities at different levels of development and complexity.
The arrangements listed below relate specifically to paediatric radiology, and are in addition
to those given for the different techniques included in earlier sections. Note that each higher
level also includes components from the lower levels.
C: Basic
•
•
•
•
•

•

Requests for each imaging procedure should include the reason for referral and relevant
clinical history of the infant/child.
Possible alternative non-ionising radiation imaging examinations should be considered.
Users should optimise equipment features and programmes for patient size and clinicaltask.
All personnel involved should understand the importance of preparation and cooperationof the child and family prior to and during imaging examinations.
Selectable pre-defined study protocols and acquisition programmes for common clinicalconditions should be available and optimised for clinical tasks performed with theequipment.
There should be a standard pregnancy policy with at least verbal and/or written questions
for adolescents when pelvic imaging is performed.

B: Intermediate•

Use pre-procedure checklists for paediatric interventional procedures, radiography andfluoroscopy (e.g., Image Gently 202b, 2020c).

•

Standard pregnancy policy that includes verbal and written questions for adolescents,
when pelvic imaging is performed.

•

Paediatric DRLs should be developed.

•

There is a standard review process to identify patients at higher risk, obtain written consent
and plan beforehand all FGI procedures.

•

There are child-friendly facilities and staff have education and training in paediatric care.

•

A process for review of near misses and safety events is enacted for peer learning.

A: Advanced•••

Advanced protocols specific to infants and children are available and regularly reviewed
by core team; and there is a process of continuous review of DRLs and achievable doses.
There is a support team for imaging that considers childcare, education, safety, quality
improvement, anaesthesia for advanced imaging, and child and family preparation.
A core team is available in paediatric units to provide protocols and techniques toadult/community-based imaging facilities. The core team shares experiences regularly
with other clinical teams, health system management, and the public.

3007

99

DRAFT REPORT FOR CONSULTATION: DO NOT REFERENCE

6. EXAMINATIONS OF PREGNANT PATIENTS

3008

3009

6.1. Introduction

3010(310) Key messages in this section:

3011
3012
3013
3014
3015

•

Medical exposure of pregnant patients requires a detailed approach to the processof justification, in which benefits and risks to both mother and the unborn childshould be taken into consideration. Imaging methods based on non-ionising radiations,e.g., ultrasound or MRI that can provide sufficient diagnostic information should
always be considered.

3016
3017
3018
3019
3020

•

Pregnant patients may be exposed either accidentally early in pregnancy or when
emergency imaging is performed prior to pregnancy status being confirmed, and inthese cases an accurate estimate of conceptus dose may be required. Web-based
software packages are available for the calculation of conceptus doses fromdiagnostic and interventional x-ray procedures.

3021
3022

•

Notices should be displayed throughout imaging facilities warning patients who
could be pregnant of the risk to the conceptus from an x-ray exposure.

3023
3024
3025

•

All female patients of childbearing potential should be questioned about pregnancy
status before the performance of x-ray examinations in which the conceptus could
be exposed - the use of a standardised form is recommended.

3026
3027

•

The use of patient shielding to reduce conceptus dose is no longer recommended forany type of diagnostic x-ray procedure.

3028
3029
3030
3031

•

Low-dose CT protocols should be established for pregnant patients for suitableclinical indications occurring during pregnancy; primary irradiation of theconceptus should be avoided and emphasis placed on limitation of scan length in the
direction of the uterus whenever possible.

3032
3033
3034

•

3035
3036
3037
3038
3039
3040
3041
3042
3043
3044
3045
3046
3047
3048
3049
3050

FGI procedures should be optimised and alternative non-ionising imaging
modalities such as sonography or MRI considered to accomplish the clinical purpose
with reduction in dose to both the conceptus and mother.
(311) Utilisation rates of x-ray imaging in pregnant patients have increased due to the rapid
evolution of medical technology, its improved usability, and enhanced accessibility (Lazarus etal., 2009; Goldberg-Stein et al., 2011; Woussen et al., 2016; Kwan et al., 2019). Publication
103 (ICRP, 2007b) defined the two source-related principles of radiological protection,
justification and optimisation, and all medical exposures of pregnant patients must be subject
to these in order to minimise exposure of the embryo or fetus. In this section the term
‘conceptus’ is used to describe all prenatal tissues from the moment of conception until birth,thus including both the embryo and fetus.
(312) Although trauma is the most common condition occurring in pregnant women, and thisoften leads to imaging, they also have several medical conditions that occur more frequently
than in women of similar age who are not pregnant. Pulmonary embolism is the most common
cause of death in pregnant women, accounting for 20% of deaths. Other serious conditions
include cerebrovascular disease, cardiac disease, and bleeding, all of which use complex
imaging procedures. Alternative, non-ionising imaging (ultrasound and magnetic resonanceimaging (MRI)) are more frequently used in these patients to avoid conceptus exposure toionising radiation.
100

DRAFT REPORT FOR CONSULTATION: DO NOT REFERENCE

3051

6.2 . Performance of x-ray procedures on pregnant patients3052

6.2.1. Justification Issues Unique to Pregnant Women

3053
3054
3055
3056
3057
3058
3059
3060
3061
3062
3063
3064
3065
3066
3067
3068
3069
3070
3071
3072
3073
3074
3075
3076
3077
3078
3079
3080
3081
3082
3083
3084
3085
3086

(313) Diagnostic and interventional x-ray examinations require that the radiologist in
consultation with the referring physician, justifies that the expected diagnostic benefits of the
exposure outweigh the potential risks for the patient, in this case a balance of effects to themother and conceptus. Publication 84 states that ‘After a type of examination or therapy has
been justified generally, each specific instance should be justified’. Therefore, a detailed
approach is required to the process of justification for exposures of pregnant patients, in which
benefits and risks to both mother and the unborn child should be taken into consideration.
Imaging methods based on non-ionising radiations, e.g., ultrasound or MRI that can provide
sufficient diagnostic information should always be considered. As an example, a standard PA
and lateral chest radiograph protocol may be justified in a 25-year-old female, but modification
may be needed for a pregnant 25-year-old to a single PA chest radiograph or chest sonography.
(314) In many cases, the mother may benefit from the exposure, but there is no direct benefit
for the exposed conceptus. However, a healthy mother means a healthy new-born. If theconceptus does not lie within the primary beam and the dose is low, then the risk will beminimal. In that case, the most important thing is to observe good radiological protection
practice.
(315) The situation is different if the conceptus is exposed primarily to radiation. When adiagnostic or interventional radiologic procedure is medically indicated, then the risk to themother of not doing the procedure will almost always outweigh the risk of harm to theconceptus. Multiple CT examinations (and fluoroscopic IR procedures) may be involved, suchas in cases of serious traumatic injuries of pregnant patients, resulting in conceptus doses
greater than 50 mGy (Raptis et al., 2014); however, this may be justified to save the mother’slife. Although the imaging management of the pregnant trauma patient should in most cases be
the same as for any other patient, there is an added need to balance the medical imaging needsof the mother and the conceptus. Therefore, particular attention needs to be paid to radiologicalprotection ethics, as well as justification, and optimisation issues in this situation.
(316) The gestational period should also be taken into account during the justification processsince the same type of examination may result in a high or low conceptus dose depending on
the size and location of the conceptus in relation to the primary x-ray beam. For example, anupper abdomen CT examination performed during the first post-conception weeks may resultin a conceptus dose below 1 mSv, whereas the dose from the same type of examination may behigher than 10 mSv at the third trimester (Damilakis et al., 2010b). Evidence-based guidelines
are needed to assist referring physicians in taking the most appropriate decisions regarding xray imaging during pregnancy.

3087

6.2.2. Optimisation Issues Unique to the Pregnant Patient

3088
3089
3090
3091
3092
3093
3094
3095

(317) Patient positioning should be a special focus for pregnant patients as they cannot lay
flat on their back for any length of time in the later stages of pregnancy. Triangular wedge
cushioning behind their right side to relieve pressure on the inferior vena cava is important;they may also have gastrointestinal reflux and require multiple pillows under their upper backand head.
(318) When a pregnant patient undergoes an x-ray examination, the exposure should be
optimised. The purpose of optimising diagnostic and interventional x-ray procedures
performed on pregnant patients is to minimise the dose of both the expectant mother and101

DRAFT REPORT FOR CONSULTATION: DO NOT REFERENCE

3096
3097
3098
3099
3100
3101
3102
3103

conceptus without affecting image quality. Pregnant patients may also be exposed accidentally
during the first weeks of gestation. A group of females likely to be exposed accidentally are
women with irregular cycles. In fact, approximately 1% of women are exposed toabdominopelvic radiation in the first trimester before they realise they are pregnant. In thesecases, pelvic ultrasound for conceptus dating and an accurate conceptus dose estimate may beneeded for patient counselling and reassurance. Fetal doses below 100 mGy should never beconsidered a reason for terminating a pregnancy (ICRP, 2000a), and doses of this magnitude
or higher should never occur following any diagnostic exposure.

3104

6.3. Methods for estimating conceptus dose

3105
3106
3107
3108
3109
3110
3111
3112
3113
3114
3115
3116
3117
3118
3119
3120
3121
3122
3123
3124
3125
3126
3127
3128
3129
3130
3131
3132
3133
3134
3135
3136
3137
3138
3139
3140
3141

(319) Pregnant patients may be exposed either accidentally early in pregnancy or when
emergency imaging is performed prior to pregnancy status being confirmed, and in these cases
an accurate estimate of conceptus dose may be required. Web-based software packages areavailable for the calculation of conceptus doses from diagnostic and interventional x-ray
procedures.
(320) Monte Carlo (MC) simulations are used to estimate conceptus doses from a variety ofdiagnostic x-ray examinations performed using a range of exposure factors. A method has beendeveloped to provide normalised dose data to estimate conceptus dose from anteroposterior(AP) and posteroanterior (PA) abdominal radiographic and fluoroscopic exposures during alltrimesters of gestation (Damilakis et al., 2002a). This method is useful not only in cases ofintentional use of radiation during pregnancy but also for accidental exposures. Radiography
and fluoroscopy are essential tools for the clinical management of pregnant patients in cases oftrauma but also for the diagnosis and treatment of other acute conditions such as haemorrhage
from splenic aneurysm or intracranial arteriovenous malformation, renal obstruction fromstones, choledocholithiasis and placenta accreta. Studies have been published describing
methods to estimate dose to a conceptus from cardiac ablation, endoscopic retrograde
cholangiopancreatography and prophylactic hypogastric artery balloon occlusion procedures(Damilakis et al., 2001; Samara et al., 2009; Solomou et al., 2016).
(321) CT is an important imaging method not only for the general population but also forpregnant patients. When MRI is not immediately available, suspected appendicitis afterinconclusive ultrasonography as well as bowel obstruction, and trauma are examples ofindications for abdominopelvic CT of the pregnant patient. Other indications include acutemental status changes from cerebral haemorrhage, pulmonary embolism, tumour, and cardiac
conditions. Methods have been developed for conceptus dose estimation from standard
abdominopelvic CT during the first post-conception weeks (Damilakis et al., 2010a) and during
the three trimesters of gestation (Angel et al., 2008). Another study has produced normalised
dose data, which allow for the estimation of conceptus dose from any CT examination
performed on the trunk of the mother (Damilakis et al., 2010b). Conceptus Dose Estimation(CoDE, 2021) is a web-based, freely available software package developed to calculate
conceptus doses and radiogenic risks associated with diagnostic and interventional x-ray
examinations carried out on pregnant patients. Another software package developed for
estimating fetal doses from CT scans (Saltybaeva et al., 2020) is also available through the web(Alkadhi and Saltybaeva, 2022).
(322) Using data provided by these packages, conceptus dose can either be anticipated so thatthe dose to the unborn child is kept to a minimum or estimated after the procedure to help thereferring physician and the patient make informed decisions regarding the management ofpregnancy. Angel et al.(2008) found that the fetal dose from a typical abdominal and pelvic CT
102

DRAFT REPORT FOR CONSULTATION: DO NOT REFERENCE

3142
3143

ranged from 16 mGy to 31 mGy with a mean value of 24 mGy. These doses should be lower
with modern scanners and optimised protocols.

3144

6.4. Pregnancy assessment before radiologic examinations

3145
3146
3147
3148
3149
3150
3151
3152
3153
3154
3155
3156
3157
3158
3159
3160
3161
3162
3163
3164
3165
3166
3167
3168
3169
3170
3171
3172

(323) When emergency x-ray imaging is needed, the examination should be carried out
without delay. Pregnancy status should be obtained as soon as possible after the imaging anddisclosed with the radiation exposure significance to the patient and family.
(324) To minimise the frequency of unintended exposures, notices and/or posters should be
displayed in the patients’ waiting room and other areas of the x-ray department warning patients
who could be pregnant of the risk to the conceptus from an x-ray exposure. Example text: “Ifyou are pregnant or you think you may be pregnant, please inform the doctor or
technologist/radiographer before the exam". A picture or illustration of pregnancy will clarify
the message and gain more attention to the sign.
(325) All female patients of childbearing potential should be questioned about pregnancy
status before x-ray examinations of the trunk are performed using a standardised form. Whennecessary, thorough investigation of pregnancy status may be needed and should include
menstrual history (Damilakis, 2020). If there is uncertainty or when direct exposure of theabdomen/pelvis with CT or interventional procedure is planned, a urine pregnancy test may berequired to determine pregnancy status. In case of a negative result, there should be nohesitation in performing the study.
(326) Adolescent girls 12–18 years old need also to be asked about their menstrual history
and pregnancy status; however, they are particularly vulnerable to social and parental pressuresand therefore, there is always a possibility that an adolescent does not provide clear answers.
In that case, minors can be asked to undergo a urine pregnancy test prior to CT andfluoroscopically-guided interventional (FGI) procedures involving direct exposure of theabdominopelvic area as well as prior to PET/CT (ACR-SPR, 2018).
(327) The above are general guidelines regarding pregnancy screening before imaging
potentially pregnant females. International and national guidelines are needed to address
several issues associated with pregnancy assessment before radiologic examinations(Applegate, 2007). Establishing screening protocols using a multidisciplinary approach andtaking into consideration local circumstances is essential to guide clinicians and radiologists
and avoid accidental exposures.

3173

6.5. Protective shielding of the conceptus

3174
3175
3176
3177
3178
3179
3180
3181
3182
3183
3184

(328) The use of patient shielding has been proposed as a means to reduce conceptus dosefrom scattered radiation coming from the x-ray tube and examination table, but is now nolonger generally recommended. A position statement, the AAPM recommended
discontinuation of the use of such shielding (AAPM, 2019c), and this issue is considered in
Section 2.3.4 and discussed at length in Hiles et al. (2020, 2021). The effectiveness of placing
radiological protection garments over part of a patient is limited because most of the conceptus
dose from extra abdominal examinations results from internal scatter within the maternal
tissues. However, pregnant patients undergoing diagnostic radiography examinations may
sometimes request contact shielding for an examination outside the pelvic region, and in suchcases provision of this shielding may offer reassurance and, if in accordance with written
procedures, could be at the discretion of the radiographer or imaging facility. Here, accurate
103

DRAFT REPORT FOR CONSULTATION: DO NOT REFERENCE

3185
3186
3187
3188
3189
3190
3191
3192

collimation is important, and the shielding must not overlay the AEC detectors.
(329) The use of patient shielding to reduce conceptus dose is no longer recommended for
fluoroscopic or CT procedures. In some cases, the use of conceptus shielding may affectnegatively the efficacy of the CT exam. It may elevate the x-ray output considerably, if part ofthe shield is inside the exposed volume, increasing the dose to the patient and her fetus, or may
produce artefacts in the CT images if placed within the overscan region of a helical scan,outside the region to be reconstructed (Hiles et al. 2020, 2021). Attention should therefore be
paid to minimising scan length rather than the use of shielding.

3193

6.6. Optimisation of x-ray procedures for pregnant patients

3194

6.6.1. Radiography

3195
3196
3197
3198
3199
3200
3201
3202
3203
3204
3205
3206
3207
3208
3209
3210
3211
3212
3213
3214
3215
3216
3217
3218
3219
3220
3221
3222
3223
3224
3225
3226
3227
3228
3229

(330) Radiation risks to a conceptus associated with radiographs performed on the mother are
negligible, unless these are repeatedly performed on the abdomen, lumbosacral spine, andpelvis. Nevertheless, the application of dose reduction protocols and techniques during
radiography is always ethical practice (ICRP, 2018a). These include adequate x-ray tube
filtration, selection of appropriate exposure parameters that result in an acceptable image
quality, correct field size, careful collimation of the x-ray beam, proper use or removal of theanti-scatter grid, utilisation of the most dose efficient x-ray equipment available and carefulselection of the x-ray projection. Protocols that are adjusted to limit the initial number ofradiographs for the clinical indication remain common for pregnant patients; a common
example is for a single view of the abdomen or chest rather than two views; if the radiologist
determines that more are justified, then they will ask for more. In addition, the PA chest
projection is associated with less dose to the conceptus than the AP projection (Damilakis etal., 2002a) as the conceptus is further from the surface on which x-rays are incident. A PA
projection will also minimise the dose to the breast and oesophagus of the patient. The lateral
distance of the unborn child from the primary beam is also of great importance for minimisationof conceptus dose. Conceptus dose can also be reduced by carrying out a chest radiograph withthe patient standing because gravity moves the conceptus further from the x-ray field.
(331) It is well known that digital imaging for radiography has the potential for reducing
patient radiation doses. The wide dynamic range of flat panel detectors and post-processing
capabilities associated with digital radiography provide several opportunities for dose
optimisation and make most image retakes unnecessary. This is especially important for
pregnant patients who need radiographic imaging, where care should be taken to select theminimum exposure necessary for the imaging task. Strategies for dose optimisation in digitalradiology are discussed in Section 2 of this document and other information is available in theliterature (IAEA, 2011).
(332) Occasionally, bone mineral density (BMD) assessment is considered beneficial during
pregnancy to identify pregnancy-associated osteoporosis and exclude diseases that present
similar clinical features. Conceptus dose from a PA spine and femur dual x-ray absorptiometry(DXA) is lower than the average daily natural background in the USA of 8 μGy during alltrimesters of gestation (Damilakis et al., 2002b). Nevertheless, all measures need to be taken
to optimise DXA examinations during pregnancy. Different technologies have been
implemented by manufacturers for BMD assessment. The most x-ray efficient DXA equipment
should always be used. When a DXA scan is needed during the first post-conception weeks,scanning with an empty bladder will expose the conceptus to a lower radiation dose (Damilakis
et al., 2002b).
104

DRAFT REPORT FOR CONSULTATION: DO NOT REFERENCE

3230

6.6.2. Computed Tomography

3231
3232
3233
3234
3235
3236
3237
3238
3239
3240
3241
3242
3243
3244
3245
3246
3247
3248
3249
3250
3251
3252
3253
3254
3255
3256
3257
3258
3259
3260
3261
3262
3263
3264
3265
3266
3267
3268
3269
3270
3271
3272
3273
3274
3275
3276
3277

(333) Pregnant women have unique physiology that leads to increased risks of conditions
requiring cross-sectional imaging; one example is the effect of the doubling of blood volume
that impacts the heart; also, when considering intravenous contrast and evaluation of CT
pulmonary angiography, the dilution effect can result in suboptimal examinations. Therefore,
optimisation in pregnant patients is a challenging task that requires deep knowledge of both theclinical status/indication and the specific parameters and dose reduction tools available during
data acquisition and post-processing. The establishment of specific low-dose acquisition
protocols based on clinical indications needed for pregnant patients such as urinary tract stonedisease, appendicitis, and pulmonary embolism is of paramount importance. Wheneverpossible, primary irradiation of the conceptus should be avoided. A simple and very effective
way of minimising the dose to both the patient and her growing child without affecting image
quality is scan range reduction. Examples of CT-guided procedures in pregnant patients canbe found at Image Wisely (2022b).
(334) Helical acquisition mode is superior to sequential mode mainly because of its speed.
However, helical mode is associated with extra exposure due to additional rotations needed forimage reconstruction of the first and last slice of the imaged volume (z-overscanning), which
may increase dose to peripheral regions of the scan with larger pitches (see Section 4.2.4).
Modern CT scanners use dynamic adaptive section collimation to block the dose from zoverscanning. For scanners without dynamic collimators, proper selection of beam collimation,
pitch, and reconstruction slice thickness is needed to restrict the extent of z-overscanning(Tzedakis et al., 2005). This is particularly important when the conceptus lies near the marginof the planned image volume. The relative contribution of the extra exposure due to zoverscanning may be considerable especially when the planned image volume is limited.
(335) Iterative reconstruction (IR) of image data has been introduced for CT with the aim of
reducing image noise. Advantage can be taken of IR to adjust exposure factors to lower thedose to the patient and conceptus dose while achieving a similar level of image quality tofiltered back-projection reconstruction (Section 4.3). The use of IR is recommended for CT
examinations of pregnant patients. Patient centring affects both patient dose and image quality.
Although pregnant patient centring errors do not affect conceptus dose significantly, improperalignment may affect image quality adversely (Solomou et al., 2015). It is, therefore,
recommended that pregnant patients are always accurately aligned at the gantry isocentre.
(336) Several CT dose reduction tools have been developed during recent years for themodulation of tube current and x-ray tube potential. Automatic tube current modulation(ATCM) tools tailor the tube current on the basis of each patient’s body habitus to produce
images of diagnostic quality at the minimum possible radiation dose (see Section 4.4).
Conceptus dose may be considerably reduced when the ATCM tool is activated (Solomou etal., 2015). CT manufacturers have recently combined ATCM tools with automatic tube voltage
selection algorithms that allow for automatic selection of x-ray tube potential and tube current
settings. No published data exist on the effect of these systems on radiation dose and image
quality in CT examinations performed on pregnant patients and, for this reason, this option
should be used with great caution when imaging pregnant patients. To minimise radiation doseto superficial dose-sensitive organs such as the eyes, thyroid and breasts, organ-based tube
current modulation systems reduce the x-ray tube output over the anterior part of the patient’s
body circumference. The effect of these systems on radiation dose to tissues and organs locatedin the central area of a patient’s body, such as the conceptus, is not known. Activation of organbased tube current modulation systems during abdominal CT exams is not recommended.
(337) It should always be borne in mind that CT scanning in the pregnant patient, especially
105

DRAFT REPORT FOR CONSULTATION: DO NOT REFERENCE

3278
3279
3280
3281
3282
3283
3284
3285
3286
3287
3288
3289
3290
3291
3292
3293
3294
3295
3296
3297
3298
3299
3300
3301
3302
3303
3304
3305
3306
3307
3308
3309
3310
3311
3312
3313

when outside of the abdomen and pelvis, provides low amounts of internal scatter to the fetus
and can be lifesaving to both mother and fetus(338) CTPA for Pulmonary Embolism: An example for suspected pulmonary embolism
illustrates some of the issues and decisions to be made regarding the choice of imaging
technique for pregnant patients. Multispecialty guidelines suggest avoidance of ionisingradiation by using ultrasound of the lower extremity veins for evaluation of deep venous
thrombosis (DVT). If positive, then treat accordingly. If uncertainty remains, then either lungscintigraphy or CT angiography are used. While lung perfusion scintigraphy to diagnose
pulmonary embolism provides the lowest dose to the mother, it does not always provide as
much clinical information. CT pulmonary angiography (CTPA) delivers a higher dose to thebreast and lung of the pregnant patient than lung perfusion scintigraphy, but it provides moreclinical information including alternative diagnoses that are critically important (lung, cardiac)
and, often more importantly, the procedure is readily available at any time of day. For thesereasons and the continued dose lowering CT technology, CTPA is considered by many the testof choice for the diagnosis of pulmonary embolism (Leung et al., 2012; Colak et al., 2021). Of
note, however, is that maternal radiogenic cancer risks from both CT pulmonary angiography
and lung perfusion scintigraphy are very low. The decision as to whether to proceed with CTPAor scintigraphy to rule out suspected pulmonary embolism in pregnant patients often depends
on equipment availability and referring physician preferences. Α study showed that a reduced
z-axis protocol for CT pulmonary angiography in pregnancy extending from aortic arch to baseof heart can reduce radiation dose by 71% without affecting the diagnosis (Shahir et al., 2015).
More details and an example of a protocol can be found from Image Wisely (2022b).
(339) Computed tomography coronary angiography (CTCA) should be considered for
pregnant patients with suspected cardiovascular disease. All modern CT scanners are capableof varying tube current output in synchrony with the patient’s electrocardiogram. An effective
radiation dose-saving technique in CTCA is prospective ECG-triggered scanning (see Section
4.5.2). When performing CTCA examinations on pregnant patients, this technique should be
preferred over retrospective acquisition. If retrospective acquisition mode is needed, ECGbased mA modulation should be employed.
(340) CT abdomen/pelvis: Where this does affect the dose, use of pitch values less than 1.0
should be avoided in pregnant patients especially for abdominal and pelvic CT examinations.
Limiting the number of CT phases through the abdomen and pelvis will reduce conceptus dose
considerably provided that the expected diagnostic information can still be obtained withconfidence. In general, repeat scanning through the conceptus should be avoided. Box 6.1
summarises the most important ways to constrain the dose to the conceptus when performing
CT examinations.

3314

106

DRAFT REPORT FOR CONSULTATION: DO NOT REFERENCE

Box 6.1. Practical ways to control conceptus dose from CT examinations•

Avoid primary irradiation of the conceptus if at all possible•

CT scanning, in the pregnant patient, especially when outside of the abdomen and pelvis, provides
low amounts of internal scatter to the fetus and can be lifesaving to both mother and fetus•

Establish low-dose acquisition protocols based on clinical indications for pregnant patients•

Pay careful attention to minimising scan length, as reductions of 1-3 cm can reduce fetal doses
by about a quarter for chest scans and a half for scans of the upper abdomen (Hiles et al., 2020).

•

Avoid the use of pitch values less than 1.0 for scanners that adjust mAs and pitch independently,
especially for abdominal and pelvic examinations, if appropriate (see Section 4.2.4)•

Limit the number of CT phases through the abdomen and pelvis as much as possible (e.g., virtual
non-contrast technique using dual energy equipment)•

Use dose reduction tools such as ATCM with caution (see Section 4.4)•

Use iterative or deep-learning based image reconstruction and reduce exposure factors to takeaccount of the resulting improvement in image quality•

Align pregnant patients at the gantry isocentre accurately

3315

6.6.3. Optimisation in fluoroscopically-guided interventional (FGI) procedures

3316
3317
3318
3319
3320
3321
3322
3323
3324
3325
3326
3327
3328
3329
3330
3331
3332

(341) Occasionally, pregnant patients are exposed to ionising radiation from FGI procedures
such as endovascular coiling in trauma, vascular dissection or malformation bleeding,
percutaneous aspiration or removal of symptomatic ovarian cysts/tumours, stent or
nephrostomy placements for renal obstruction from stones, radiofrequency cardiac catheter
ablation and endoscopic retrograde cholangiopancreatography. Alternative non-ionising
imaging modalities such as ultrasound or MRI should be considered to accomplish the clinicalpurpose, where possible.
(342) Optimisation of all FGI procedures is needed to accomplish the clinical purpose withthe maximum possible dose reduction for the conceptus and the mother. The same applies to
CT guided interventions. FGI procedures in the anatomic regions of the thorax, head/neck andthe extremities are associated with low conceptus dose (McCollough, 2007). For example, atypical catheter ablation procedure performed on young female patients requiring 0.58, 23, 5.3
and 10.2 minute exposures for groin-to-heart PA, PA, right anterior oblique, and left anterior
oblique projections, respectively, is associated with a conceptus dose lower than 1 mGy during
all trimesters of gestation (Damilakis et al., 2001). If the conceptus is likely to be in, or proximal
to, the primary beam, conceptus doses can be much higher. Ways in which the operator can
reduce the dose to the conceptus when performing FGI procedures are listed in Box 6.2.

3333

107

DRAFT REPORT FOR CONSULTATION: DO NOT REFERENCE

Box 6.2. Practical ways to control conceptus dose during FGI procedures

3334
3335
3336
3337
3338
3339
3340
3341
3342

•

Collimate the beam carefully•

Keep the exposure time as short as possible•

Use as high a tube potential as possible•

Avoid overuse of the magnification mode•

Keep the x-ray tube as far away from the patient as possible and the detector close to the patient•

Use low-dose-rate pulsed fluoroscopy•

Use last series hold (also referred to as video loop) when available•

Keep the dose from digital subtraction angiography to a minimum•

Consider using ultrasound guidance for catheter insertion and choose a route that reduces
conceptus dose•

Determine the optimal status of the maternal bladder in relation to the type of projections
needed for the procedure.

(343) Dose management software systems are considered important tools for ensuring patient
safety and image quality (ICRP, 2022). Information provided can be used for the selection of
the most dose-efficient equipment for the pregnant patient and the development of acquisition
protocols that deliver the lowest radiation dose to the unborn child without sacrificing
diagnostic image quality. While patient exposure tracking may have several advantages, caremust be taken to make sure that conceptus dose estimation methods used by dose management
systems are appropriate and dose data analysis is performed by an experienced medical
physicist.

108

DRAFT REPORT FOR CONSULTATION: DO NOT REFERENCE

3343

7. CONCLUSIONS

3344
3345
3346
3347
3348
3349
3350
3351
3352
3353
3354
3355
3356
3357
3358
3359
3360
3361
3362
3363
3364
3365
3366
3367
3368
3369
3370
3371
3372
3373
3374
3375
3376
3377
3378
3379
3380
3381
3382
3383
3384
3385
3386
3387
3388
3389
3390

(344) Optimisation in digital radiology requires provision of clinical images for individual
patients that are of sufficient quality to ensure accurate and reliable diagnosis to enable correctcare decisions to be made. The radiation doses used to acquire the clinical images should be
adjusted to the minimum level appropriate—and locally available—for the imaging technology,
clinical indication, and individual patient’s needs. This report brings together practical aspects
of optimisation of radiological protection for the various digital radiology modalities(radiography, fluoroscopy, and CT), which all require similar approaches, but with slightly
different methods in their application.
(345) Publication 15x set out three building blocks on which strategies for achieving
optimisation should be built (ICRP, 2022). The corner stone is collaboration between
radiological professionals, with radiologists, radiographers and medical physicists working
together as a team within an organisation that provides a structure for these processes. The
radiologist can judge whether the image quality is sufficient for the diagnostic purpose, theradiographer knows the practical operation and limitations of the equipment, and the medical
physicist understands the physical principles behind image formation, and can perform andinterpret measurements of dose and image quality. Success of this collaboration depends on
members of the optimisation team recognising the skills of the other members and working
together with mutual respect in their different roles. Increasing technical and computational
complexity in radiology equipment and applications increases the importance of this multiprofessional approach and the dependency on the combined knowledge of different
professionals.
(346) This publication is aimed primarily at radiologists and other physicians, radiographers,
and medical physicists, but should also be understood by managers, all fluoroscopy operators,
regulators, equipment manufacturers, and expert societies/organisations. There will be parts
that are more suitable for one or other group. For example, in Section 2 on radiography, someparts deal with optimisation as part of the day-to-day work of the radiographer. On the other
hand, there are parts of Sections 2, 3, and 4 that deal with aspects of equipment performance
set up during commissioning, which are of more relevance to medical physicists, but that need
to be taken forward in discussion with radiologists and radiographers. There are also
approaches for interventional procedures in Section 3, which will be of prime interest to theclinicians who perform them, but of relevance to other groups.
(347) Technological innovations are being implemented continually that have the potential toprovide a higher degree of optimisation. Assessments of aspects of image quality as well asradiation dose are now used in controlling exposure levels. As the level of sophistication
develops, the variety and complexity of procedures that are possible increases. In order to makefull use of new features, the performance of equipment needs to be monitored and analysed,
and examination protocols refined as more experience is gained.
(348) The publication provides a message for management in emphasising the need for staff
to receive comprehensive initial training in the use of imaging equipment and software. It also
reinforces the requirement for the continuation of career long training to ensure that the fullpotential of new techniques, as they become available, can be realised. Management must
commit to provide both resources and organisational processes that ensure a culture of radiation
safety and of continual improvement in optimisation.
(349) Vendors need to provide sufficient information and training about operation and properuse of features that allow dose levels on new equipment to be set at optimum levels for all local
patient populations. This becomes ever more important as equipment with new features arepurchased by a wider variety of facilities. Vendors should provide an additional level of109

DRAFT REPORT FOR CONSULTATION: DO NOT REFERENCE

3391
3392
3393
3394
3395
3396
3397
3398
3399
3400
3401

assistance where equipment features are introduced for the first time into countries that may
not have the level of medical physics support and experience to ensure that the features are set
up properly at the start and used effectively thereafter.
(350) Operation of all digital radiology imaging involves the need for understanding theinterdependence of patient dose and image quality. This publication discusses these aspects
where they relate to performance of a particular type of equipment. Readers are directed to
Publication 15x for more detailed consideration of dose audit and image quality analysis (ICRP,
2022), and to Publication 135 in relation to the use of DRLs (ICRP, 2017).
(351) The key message is that continual striving for optimisation is an essential requirement
for an efficient digital radiology service. This publication provides information that should beof value to radiology staff and facilities in achieving this.

110

DRAFT REPORT FOR CONSULTATION: DO NOT REFERENCE

3402

REFERENCES

3403
3404
3405
3406
3407
3408
3409
3410
3411
3412
3413
3414
3415
3416
3417
3418
3419
3420
3421
3422
3423
3424
3425
3426
3427
3428
3429
3430
3431
3432
3433
3434
3435
3436
3437
3438
3439
3440
3441
3442
3443
3444
3445
3446
3447
3448
3449
3450
3451
3452
3453

AAPM, 2001. Cardiac Catheterisation Equipment Performance, AAPM Report Number 70. American
Association of Physicists in Medicine, New York.
AAPM, 2006. Quality assurance of computed and digital radiography systems. Acceptance Testing and
Quality Control of Photostimulable Storage Phosphor Imaging Systems. Report No. 93, AAPM Task
Group 10. American Association of Physicists in Medicine, New York.
AAPM, 2009. An exposure indicator for digital radiography, Report of AAPM Radiography andFluoroscopy Subcommittee Task Group 116. American Association of Physicists in Medicine, NewYork.
AAPM, 2011a. Size-Specific Dose Estimates (SSDE) in Pediatric and Adult Body CT Examinations.
Report of AAPM Task Group 204. American Association of Physicists in Medicine, New York.
AAPM, 2011b. Recommendations Regarding Notification and Alert Values for CT Scanners:
Guidelines for Use of the NEMA XR 25 CT Dose-Check Standard. (attention to Table 1) American
AssociationofPhysicistsinMedicine,
New
York.
Availableathttps://www.aapm.org/pubs/CTProtocols/documents/NotificationLevelsStatement.pdf,(lastaccessed August 2022).
AAPM, 2012. Functionality and Operation of Fluoroscopic Automatic Brightness Control/Automatic
Dose Rate Control Logic in Modern Cardiovascular and Interventional Angiography Systems,
AAPM Report No. 125. American Association of Physicists in Medicine, New York.
AAPM, 2014. Use of water equivalent diameter for calculating patient size and size-specific dose
estimates (SSDE) in CT Report of AAPM Task Group 220 (College Park, MD: AAPM). American
Association of Physicists in Medicine, New York.
AAPM, 2015. Ongoing quality control in digital radiography: Report of AAPM Imaging Physics
Committee Task Group 151. Med. Phys. 42(11), 6658–6670.
AAPM 2018. Considerations for the use of handheld image viewers. Report of AAPM Task Group 260.
American Association of Physicists in Medicine, New York.
AAPM, 2019a. Estimating Patient Organ Dose with Computed Tomography: A Review of Present
Methodology and Required DICOM Information. A Joint Report of AAPM Task Group 246 and theEuropean Federation of Organizations for Medical Physics (EFOMP). American Association of
Physicists in Medicine, New York . Available at https://www.aapm.org/pubs/reports/RPT_246.pdf(last accessed October 2020).
AAPM, 2019b. Performance Evaluation of Computed Tomography Systems. Report of AAPM Task
Group 233. American Association of Physicists in Medicine, New York. Available athttps://aapm.org/pubs/reports/detail.asp?docid=186, (last accessed August 2022).
AAPM, 2019c. Position Statement on the Use of Patient Gonadal and Fetal Shielding. 2019. American
AssociationofPhysicistsinMedicine,
New
York.
Availableathttps://www.aapm.org/org/policies/details.asp?id=468&type=PP (last accessed October 2020).
AAPM, 2022. The alliance for quality computed tomography. Reference CT Protocols. American
AssociationofPhysicistsinMedicine,
New
York.
Availableathttps://www.aapm.org/pubs/CTProtocols/default.asp (last accessed Jan 2022).
Achenbach, S., Marwan. M., Ropers. D., et al., 2010. Coronary computed tomography angiography
with a consistent dose below 1 mSv using prospectively electrocardiogram-triggered high-pitch
spiral acquisition. Europ. Heart J. 31, 340–346.
ACR, 2021. Manual on Contrast Media. American College of Radiology, Reston, VA. Available athttps://www.acr.org/Clinical-Resources/Contrast-Manual (last accessed 5 Jan 2022).
ACR, 2022. ACR CT Accreditation Program, American College of Radiology , Reston, VA. Available
at https://www.acraccreditation.org/modalities/ct, (last accessed August 2022).
ACR–AAPM–SIIM–SPR, 2017. Practice parameter for digital radiography. Revised 2017. American
College of Radiology, Reston, VA. Available at https://www.acr.org/-/media/ACR/Files/PracticeParameters/Rad-Digital.pdf (last accessed 5 December 2021).
ACR–SPR, 2018. Practice parameter for imaging pregnant or potentially pregnant adolescents andwomen with ionizing radiation. Resolution 39, 1–23. Available at https://www.acr.org/111

DRAFT REPORT FOR CONSULTATION: DO NOT REFERENCE

3454
3455
3456
3457
3458
3459
3460
3461
3462
3463
3464
3465
3466
3467
3468
3469
3470
3471
3472
3473
3474
3475
3476
3477
3478
3479
3480
3481
3482
3483
3484
3485
3486
3487
3488
3489
3490
3491
3492
3493
3494
3495
3496
3497
3498
3499
3500
3501
3502
3503
3504
3505
3506

/media/acr/files/practice-parameters/pregnant-pts.pdf (last accessed 15 Dec 2021).
ACR-RSNA, 2020. The radiology information resource for patients. RadiologyInfo.org. Available athttps://www.radiologyinfo.org/ (last accessed October 2020).
ACR-DIR, 2022. American College of Radiology Dose Index Registry for CT scan doses. American
College of Radiology, Reston, VA.
https://www.acr.org/Practice-Management-QualityInformatics/Registries/Dose-Index-Registry (last accessed August 2022).
Akai, H., Kiryu, S., Shibata, E., et al., 2016. Reducing CT radiation exposure with organ effective
modulation: a retrospective clinical study. Eur. J. Radiol. 85(9), 1569–1573.
Alhailiy, A.B., Ekpo, E.U., Kench, P.L., Ryan, E.A., Brennan, P.C., McEntee, M., 2019. The associatedfactors for radiation dose variation in cardiac CT angiography. Br. J. Radiol 92, 20180793.
Alkadhi, H., Saltybaeva, N., 2022. Fetal Radiation Dose Assessment. Available athttps://www.fetaldose.org/. (accessed 1st October 2022).
Alsleem, H., Davidson, R., Al-Dhafiri, B., Alsleem, R., Ameer, H. 2019. Evaluation of radiographers'
knowledge and attitudes of image quality optimisation in paediatric digital radiography in Saudi
Arabia and Australia: a survey-based study. J. Med. Radiat. Sci. 66(4), 229–237.
Angel,. E, Wellnitz, C.V., Goodsitt, M.M., et al., 2008. Radiation dose to the fetus for pregnant patients
undergoing multidetector CT imaging: Monte Carlo simulations estimating fetal dose for a range ofgestational age and patient size. Radiology 249(1), 220–227.
Applegate, K., 2007. Pregnancy screening of adolescents and women before radiologic testing: Does
radiology need a national guideline?. J. Am. Coll. Radiol. 4, 533–536.
Arellano, R.S., Yang, K., Rehani, M.M. 2021. Analysis of patients receiving ≥ 100 mSv during acomputed tomography intervention. Eur. Radiol. 31(5), 3065–3070.
Arndt, C., Güttler, F., Heinrich, A., et al., 2021. Deep Learning CT Image Reconstruction in Clinical
Practice. Rofo. 193(3), 252–261.
Aschoff, A.J., Catalano, C., Kirchin, M.A., Krix. M.,Albrecht, T., 2017. Low radiation dose in computed
tomography: the role of iodine. Br. J. Radiol. 90, 20170079.
Aufrichtig, R., Xue, P., Thomas, C.W., Gilmore, G.C., Wilson, D.L., 1994. Perceptual comparison ofpulsed and continuous fluoroscopy. Med. Phys. 21(2), 245–256.
Balter S, Fletcher D, Kuan H, et al., 2002. Techniques to estimate radiation dose to skin during
fluoroscopically guided procedures. Skin Dose Measurements AAPM, July 2002. Available athttps://www.aapm.org/meetings/02am/pdf/8368-40188.pdf., (last accessed August 2022).
Balter, S., Hopewell, J.W., Miller, D.L., Wagner, L.K., Zelefsky, M.J., 2010. Fluoroscopically guided
interventional procedures: a review of radiation effects on patients' skin and hair. Radiology 254(2),326–341.
Balter, S., 2019. Fluoroscopic Technology from 1895 to 2019. Drivers: Physics and Physiology. Medical
Physics International Journal, Special Issue, History of Medical Physics 2019, 2, 111–140.
Barrett, T., Bowden, D.J, Shaida, N., et al. 2012. Virtual unenhanced second generation dualsource CTof the liver: is it time to discard the conventional unenhanced phase?. Eur. J. Radiol. 81, 1438–1445.
Bednarek, D., Barbarits, J., Rana, V.K., Nagaraja, S.P., Josan. M.S., Rudin, S., 2011. Verification of theperformance accuracy of a real-time skin-dose tracking system for interventional fluoroscopic
procedures. Proc. SPIE Int. Soc. Opt. Eng. 7961, 638–645.
Bly, R., Järvinen, H., Kaijaluoto, S., Ruonala, V., 2020. Contemporary collective effective dose to the
population from x-ray and nuclear medicine examinations-changes over last 10 years in Finland.
Radiat. Prot. Dosim. 189(3), 318–322.
Boone, J.M., Geraghty, E.M., Seibert, J.A., Wootton-Gorges, S.L., 2003. Dose reduction in paediatric
CT: A rational approach. Radiology 228, 352–360.
Boone, J.M.., 2009. Method for evaluating bow tie filter angle‐dependent attenuation in CT: Theory
and simulation results. Med. Phys. 37, 40–48.
Boos, J., Thomas, C., Appel, E., et al., 2018. Institutional computed tomography diagnostic reference
levels based on water-equivalent diameter and size-specific dose estimates. J. Radiol. Prot. 38, 536–
548.
Bordier, C., Klausz, R., Desponds, L., 2015. Patient dose map indications on interventional X-ray
systems and validation with Gafchromic XR-RV3 film. Radiat. Prot. Dosim. 163(3), 306–318.
112

DRAFT REPORT FOR CONSULTATION: DO NOT REFERENCE

3507
3508
3509
3510
3511
3512
3513
3514
3515
3516
3517
3518
3519
3520
3521
3522
3523
3524
3525
3526
3527
3528
3529
3530
3531
3532
3533
3534
3535
3536
3537
3538
3539
3540
3541
3542
3543
3544
3545
3546
3547
3548
3549
3550
3551
3552
3553
3554
3555
3556
3557
3558
3559

Bui, A.L., Dieleman, J.L., Hamavid, H., et al. 2017. Spending on Children’s Personal Health Care in
the United States, 1996–2013. JAMA Pediatr. 171(2), 181–189.
Buls, N., Pages, J., Mana, F., Osteaux, M., 2002. Patient and staff exposure during endoscopic
retrograde cholangiopancreatography. British Journal of Radiology. 75(893), 435–443.
Busch, H.P., Faulkner, K., 2005. Image quality and dose management for digital radiography. Radiat.
Prot. Dosim. 117(1–3), 143–147.
Carroll, Q.B., 2018. Radiography in the Digital age. 3rd edition. eBooks. C.C. Thomas, Springfield.
Cartlon, R.R, Adler, A.M., 2013. Principles of radiographic imaging: an art and a science. Clifton Park,
NewYork.
CoDE , 2021. Concert: Conceptus radiation doses and risks from imaging with ionizing radiation.
University of Crete, Heraklion. Available at http://embryodose.med.uoc.gr/ (last accessed 17 Dec
2021).
Cohen, M.D., Cooper, M.L., Piersall, K., Apgar, B.K., 2011. Quality assurance: Using the exposureindex and the deviation index to monitor radiation exposure for portable chest radiographs inneonates. Pediatr. Radiol. 41, 592–601.
Colak, E., Kitamura, F.C., Hobbs, A.B. et al., 2021. The RSNA Pulmonary Embolism CT Dataset.
Radiol. Artif Intell. 3(2), e200254.
COMARE, 2021 Radiological dose issues with interventional radiology within the UK. Committee On
Medical Aspects of Radiation in the Environment 19th Report, Chilton, PHE. Available athttps://www.gov.uk/government/publications/radiological-dose-issues-with-interventionalradiology-in-he-uk (last accessed 29 Dec 2021).
CTisus, 2022. Everything you need to know about Computed Tomography (CT) & CT Scanning. CT
Scan Protocols. https://www.ctisus.com/responsive/protocols. (last accessed 6 Jan 2022).
Curry, T., Dowdey, J., Murry, R.. 1990. Christensen's Physics of Diagnostic Radiology. Lippincott
Williams & Wilkins, Philadelphia, PA, 93–98.
Damilakis, J., Theocharopoulos, N., Perisinakis, K., et al., 2001. Conceptus radiation dose and risk fromcardiac catheter ablation procedures. Circulation 104, 893–897.
Damilakis, J., Perisinakis, K., Vrahoriti, H., Kontakis, G., Varveris, H., Gourtsoyiannis, N., 2002.
Embryo/fetus radiation dose and risk from dual X-ray absorptiometry examinations. Osteoporos. Int.
13, 716–722.
Damilakis, J., Tzedakis, A., Sideri, L., Perisinakis K, Stamatelatos I, Gourtsoyiannis N., 2002.
Normalized conceptus doses for abdominal radiographic examinations calculated using a Monte
Carlo technique. Med. Phys. 29, 2641–2648.
Damilakis, J., Perisinakis, K., Tzedakis, A., Papadakis, A., Karantanas, A., 2010a. Radiation dose to theembryo from NDCT during early gestation: A method that allows for variations in maternal bodysize and embryo position. Radiology 257, 483–489.
Damilakis, J., Tzedakis, A., Perisinakis, K., Papadakis, A.E., 2010b. A method of estimating embryo
doses resulting from multidetector CT examinations during all stages of gestation. Med. Phys. 37,
6411–6420.
Damilakis, J., 2020. The management of (a) pregnant patients and (b) pregnant employees. In:
Damilakis, J (Editor), Radiation dose management of pregnant patients, pregnant staff and paediatricpatients. Diagnostic and interventional radiology. IOP Publishing, Bristol, pp. 8-1-8.10
D'Angelo, T., Cicero, G., Mazziotti, S., et al., 2019. Dual energy computed tomography virtualmonoenergetic imaging: technique and clinical applications. Br. J. Radiol. 92(1098), 20180546.
Dauer, L.T., Thornton, R.H., Miller, D.L., et al., 2012. Radiation management for interventions using
fluoroscopic or computed tomographic guidance during pregnancy: a joint guideline of the Societyof Interventional Radiology and the Cardiovascular and Interventional Radiological Society ofEurope with Endorsement by the Canadian Interventional Radiology Association. J. Vasc. Interv.
Radiol. 23(1), 19–32.
Dave, J.K., Jones, A.K., Fisher, R. et al., 2018. Current state of practice regarding digital radiography
exposure indicators and deviation indices: Report of AAPM Imaging Physics Committee Task Group
232. Med. Phys. 45 (11), e1146–e1160.
Dixon, M.T., Loader, R.J., Stevens, G.C., Rowles, N.P., 2016. An evaluation of organ dose modulation
113

DRAFT REPORT FOR CONSULTATION: DO NOT REFERENCE

3560
3561
3562
3563
3564
3565
3566
3567
3568
3569
3570
3571
3572
3573
3574
3575
3576
3577
3578
3579
3580
3581
3582
3583
3584
3585
3586
3587
3588
3589
3590
3591
3592
3593
3594
3595
3596
3597
3598
3599
3600
3601
3602
3603
3604
3605
3606
3607
3608
3609
3610
3611
3612

on a GE optima CT660-computed tomography scanner. J. Appl. Clin. Med. Phys. 17(3), 380–391.
Don, S., 2004. Radiosensitivity of children: potential for overexposure in CR and DR and magnitudeof doses in ordinary radiographic examinations. Pediatr. Radiol. 34, S167–S172.
Donnelly, L.F., Kathleen, H., Emery, et al., 2001. Minimizing Radiation Dose for Pediatric Body
Applications of Single-Detector Helical CT. Am. J. Roentgenol 176, 303–306.
Dorfman, A.L., Fazel, R., Andrew, J., et al., 2011. Use of Medical Imaging Procedures With Ionizing
Radiation in Children: A Population-Based Study. Arch. Pediatr. Adolesc. Med. 165(5), 458–464.
Dovales, A.C.M, da Rosa, L.A.R., Kesminiene, A., et al., 2016. Patterns and trends of computed
tomography usage in outpatients of the Brazilian public healthcare system, 2001–2011. J. Radiol.
Prot. 36, 547–560.
Doyle, P., Martin, C.J., 2006. Calibrating automatic exposure control devices for digital radiography.
Phys. Med. Biol. 51, 5475–5485.
Eberhard, M., Mergen, V., Higashigaito, K. et al. 2021. Coronary Calcium Scoring with First Generation
Dual-Source Photon-Counting CT-First Evidence from Phantom and In-Vivo Scans. Diagnostics(Basel). 11(9), 1708.
EC, 1995. European guidelines on quality criteria for diagnostic radiographic images. EUR 16260 EN.
European Commission, Brussels.
EC, 2004. Image Quality and Dose Management For Digital Radiography. DIMOND III Report.
European Commission, Brussels. Available at https://www.sorf.fi/doc/diamond_III.pdf. (lastaccessed October 2019).
EC, 2012. Criteria for Acceptability of Medical Radiological Equipment used in Diagnostic Radiology,
Nuclear Medicine and Radiotherapy. Radiation Protection Report no. 162. European Commission,
Luxembourg.
EFOMP-ESTRO-IAEA, 2019 Quality control in cone-beam computed tomography (CBCT), EFOMPESTRO-IAEA protocol. European Federation of Organisations for Medical Physics, Utrecht.
Available at https://www.efomp.org/uploads/2d23d153-b77c-4161-802c5b8422d15e29/EFOMP_IAEA_ESTRO_%20CBCT_2019_05_27.pdf (last accessed July 2020).
Ekpo, E.U., Adejoh, T., Akwo, J.D., et al., 2018. Diagnostic reference levels for common computed
tomography (CT) examinations: results from the first Nigerian nationwide dose survey. J. Radiol.
Prot. 38, 525–535.
Esteva, A., Robicquet, A., Ramsundar, B., K. et al., 2019. A guide to deep learning in healthcare. Nat.
Med. 25(1), 24–29.
ESR, 2020. Eurosafe Imaging Website. European Society of Radiology, Viena. Available at
http://www.eurosafeimaging.org/ (last accessed October 2020).
EU, 2018. European Guidelines on Diagnostic reference Levels for Paediatric Imaging (PiDRLs).
Radiation
Protection
No.185.
European
Union,
Luxembourg.
Availableat
http://www.eurosafeimaging.org/pidrl, (last accessed August 2022).
Fang ,T., Deng, W., Law, MW-M., et al., 2018. Comparison of image quality and radiation exposure
between conventional imaging and gemstone spectral imaging in abdominal CT examination. Br. J.
Radiol. 91, 20170448.
Farah, J., Trianni, A., Ciraj-Bjelac, O., et al., 2015. Characterization of XR-RV3 GafChromic(®) films
in standard laboratory and in clinical conditions and means to evaluate uncertainties and reduce
errors. Med. Phys. 42(7), 4211–4226.
Fernandez-Soto, J.M., Ten, J.I., Sanchez, R.M., España. M., Pifarre. X., Vano. E., 2015. Benefits of an
automatic patient dose registry system for interventional radiology and cardiology at five hospitalsof the Madrid area. Radiat. Prot. Dosim. 165(1-4), 53–56.
Filev, P.D., Mittal, P.K., Tang, X. et al., 2016. Increased Computed Tomography Dose Due toMiscentering With Use of Automated Tube Voltage Selection: Phantom and Patient Study. Curr. Probl.
Diagn. Radiol. 45, 265–270.
Fisher, R.F., Applegate, K.E., Berkowitz, L.K. et al., 2021. AAPM Medical Physics Practice Guideline
12.a: Fluoroscopy dose management. J. Appl. Clin. Med. Phys. 23(1), e13526.
Fletcher, D.W., Miller, D.L., Balter, S., Taylor, M.A., 2002. Comparison of four techniques to estimate
radiation dose to skin during angiographic and interventional radiology procedures. J. Vasc. Interv.
114

DRAFT REPORT FOR CONSULTATION: DO NOT REFERENCE

3613
3614
3615
3616
3617
3618
3619
3620
3621
3622
3623
3624
3625
3626
3627
3628
3629
3630
3631
3632
3633
3634
3635
3636
3637
3638
3639
3640
3641
3642
3643
3644
3645
3646
3647
3648
3649
3650
3651
3652
3653
3654
3655
3656
3657
3658
3659
3660
3661
3662
3663
3664
3665

Radiol. 13(4), 391–397.
Flohr, T., Petersilka, M., Henning, A., Ulzheimer, S., Ferda, J., Schmidt, B. 2020. Photon-counting CT
review. Phys. Med. 79, 126–136.
Foster, L.P., Clark, K.R. 2019. Pediatric Radiography Education: A Survey of Recent Graduates'
Experiences. Radiol Technol. 91(1), 18–26.
George, E., Wortman, J.R., Fulwadhva, U.P., Uyeda, J.W., Sodickson, A.D., 2017. Dual energy CT
applications in pancreatic pathologies. Br. J. Radiol. 90, 20170411.
Gibson, D.J., Davidson, R.A., 2012. Exposure Creep in Computed Radiography: A Longitudinal Study.
Academic Radiology 19, 458–462.
Goldberg-Stein, S., Liu, B., Hahn, P.F., et al., 2011. Body CT during pregnancy: utilization trends,
examination indications, and fetal radiation doses. Am. J. Roentgenol. 196, 146–151.
Goske, M.J., Charkot, E., Herrmann, T., et al., 2011. Image Gently: challenges for radiologic
technologists when performing digital radiography in children. Pediatr. Radiol. 41, 611–619.
Gottumukkala, R.V., Kalra, M.K., Tabari, A., Otrakji. A., Gee, M.S., 2019. Advanced CT Techniques
for Decreasing Radiation Dose, Reducing Sedation Requirements, and Optimizing Image Quality inChildren. Radiographics 39(3),709–726.
Graser, A., Johnson, T.R.C, Hecht, E.M., et al., 2009. Dual-energy CT in patients suspected of having
renal masses: Can virtual non-enhanced images replace true non-enhanced images?. Radiology
252(2), 433–440.
Greffier, J., Van Ngoc Ty, C., Agelou, M., et al., 2017. Impact of the calibration conditions of XR-RV3
films on peak skin dose measurements in interventional radiology. Radiat. Prot. Dosim. 174(2), 207–
215.
Hara, A.K., Paden, R.G., Silva, A.C., Kujak, J. L., Lawder, H. J., Pavlicek, W., 2009. Iterative
reconstruction technique for reducing body radiation dose at CT: feasibility study. Am. J. Roentgenol.
193, 764–771.
Hart, D., Wall, B.F., Hillier, M.C., Shrimpton, P.C., 2010. Frequency and collective dose for medical
and dental x-ray examinations in the UK 2008 Report HPA-CRCE-012, Chilton, HPA.
Hassan, A., Nazir, S.A., Alkadhi, H., 2011. Technical challenges of coronary CT angiography: today
and tomorrow. Eur. J. Radiol. 79(2), 161–171.
Health IT, 2013. Shared decision making. The Office of the National Coordinator for Health
Information Technology, Washington, DC. Available athttps://www.healthit.gov/sites/default/files/nlc_shared_decision_making_fact_sheet.pdf (lastaccessed 26 Jan. 2022).
Heaney, D.E., Norvill, A.J., 2006. A comparison of reduction in CT dose through the use of gantry
angulations or bismuth shields. Australas. Phys. Eng. Sci. Med. 29,172–178.
Herrmann, T.L., Fauber, T.L., Gill, J., et al., 2012. Best practices in digital radiography. Radiol. Technol.
84(1), 83–89.
Hiles, P., Sullivan, Y., Benson, E. et al., 2020. Guidance on using shielding on patients for diagnostic
radiology applications. British Institute of Radiology, London.
Hiles, P., Gilligan, P., Damilakis, J. et al. 2021. European consensus on patient contact shielding.
Insights Imaging 12, 194.
Hoang, J.K., Yoshizumi, T.T., Choudhury, K.R., et al., 2012. Organ based dose current modulation andthyroid shields: Techniques of radiation dose reduction for neck CT. Am. J. Roentgenol. 198(5),1132–1138.
Hoeffner, E.G.,Case, I., Jain, R. et al, 2004. Cerebral Perfusion CT: Technique and Clinical Applications.
Radiology 231(3), 632–644.
Hsieh, J., Flohr, T. 2021. Computed tomography recent history and future perspectives. J. Med. Imag.
8(5), 052109.
Husmann, L., Valenta, I., Gaemperli, O., Adda, O., Treyer, V., Wyss, C.A., 2008. Feasibility of lowdose coronary CT angiography: first experience with prospective ECG-gating. Eur. Heart J. 29, 191–
197.
IAEA, 2007. Dosimetry in Diagnostic Radiology: An International Code of Practice, Technical Reports
Series No. 457, International Atomic Energy Agency, Vienna.
115

DRAFT REPORT FOR CONSULTATION: DO NOT REFERENCE

3666
3667
3668
3669
3670
3671
3672
3673
3674
3675
3676
3677
3678
3679
3680
3681
3682
3683
3684
3685
3686
3687
3688
3689
3690
3691
3692
3693
3694
3695
3696
3697
3698
3699
3700
3701
3702
3703
3704
3705
3706
3707
3708
3709
3710
3711
3712
3713
3714
3715
3716
3717
3718

IAEA, 2010. Patient dose optimization in fluoroscopically guided interventional procedures: final
report of a coordinated research project. IAEA TECDOC 1641, International Atomic Energy Agency,
Vienna.
IAEA, 201.1 Avoidance of unnecessary dose to patients while transitioning from analogue to digitalradiology. IAEA-TECDOC-1667, International Atomic Energy Agency, Vienna.
IAEA/WHO 2012 Radiation protection in medicine: setting the scene for the next decade Proc. Int.
Conf. 3–7 December 2012, Bonn, Germany.Availabe athttps://rpop.iaea.org/RPOP/RPoP/Content/AdditionalResources/Bonn_Call_for_Action_Platform/(last accessed 4 Jan. 2022).
IAEA 2015 Worldwide implementation of digital imaging in radiology. Human Health Series No. 28,
IAEA 1647, International Atomic Energy Agency, Vienna.
IAEA, 2020 radiation protection of patients (RPOP) . International Atomic Energy Agency, Vienna.
Availabe at https://www.iaea.org/resources/rpop, (last accessed Aiugust 2022).
IAEA, 2022 Children and radiation-what patients need to know. Radiation Protection of Patients.
International Atomic Energy Agency, Vienna. Availabe athttps://www.iaea.org/resources/rpop/patients-and-public/children (last accessed 22 Jan 2022).
IAEA SAFRAD, XXXX. Safety in Radiological Procedures. International Atomic Energy Agency,
Vienna. Availabe at https://www.iaea.org/resources/rpop/resources/databases-and-learningsystems/safrad, (last accessed August 2022).
Ichimoto, E., Kadohira, T., Nakayama, T., De Gregorio. J., 2018. Efficacy of radiation dose reduction
due to real-time monitoring and visualization of peak skin dose during coronary angiography andpercutaneous coronary intervention. Catheter Cardiovasc Interv. 91(4), 717–722.
ICRP, 1982 Protection of the patient in diagnostic radiology. Publication 34, Ann. ICRP 9(2-3).
ICRP, 1991. 1990 Recommendations of the International Commission on Radiological Protection.
Publication 60. Ann. ICRP 21(1–3).
ICRP, 1996. Radiological protection and safety in medicine. ICRP Publication 73. Ann. ICRP 26(2).
ICRP, 2000a. Pregnancy and medical radiation. Publication 84, Ann. ICRP 30(1).
ICRP, 2000b. Avoidance of radiation injuries from interventional procedures. ICRP Publication 85. Ann.
ICRP 30(2).
ICRP, 2000c. Managing Patient Dose in Computed Tomography. ICRP Publication 87, Ann. ICRP 30(4)ICRP, 2004. Managing patient dose in digital radiology. ICRP Publication 93, Ann. ICRP 34(1).
ICRP, 2006 The Optimisation of Radiological Protection: Broadening the Process. Publication 101b.
Ann. ICRP 36(3)ICRP, 2007a. Managing patient dose in multi-detector computed tomography (MDCT). ICRP
Publication 102. Ann ICRP 37(1).
ICRP, 2007b. The 2007 Recommendations of the International Commission on Radiological Protection.
ICRP Publication 103. Ann. ICRP 37(2–4).
ICRP, 2009. Education and training in radiological protection for diagnostic and interventional
procedures. Publication 113. Ann. ICRP 39(5).
ICRP, 2010. Radiological Protection in Fluoroscopically Guided Procedures Performed Outside the
Imaging Department. Publication 117, Ann. ICRP 40(6).
ICRP, 2012 ICRP Statement on Tissue Reactions / Early and Late Effects of Radiation in Normal
Tissues and Organs – Threshold Doses for Tissue Reactions in a Radiation Protection Context. ICRP
Publication 118. Ann. ICRP 41(1/2).
ICRP, 2013a. Radiological protection in cardiology. ICRP Publication 120. Ann ICRP 42(1).
ICRP, 2013b. Radiological protection in paediatric diagnostic and interventional radiology. ICRP
Publication 121. Ann. ICRP 42(2).
ICRP, 2015. Radiological Protection in Cone Beam Computed Tomography (CBCT). ICRP Publication
129, Ann. ICRP 44(21).
ICRP, 2017. Diagnostic Reference Levels in Medical Imaging. ICRP Publication 135, Ann. ICRP 46(1).
ICRP, 2018a. Ethical Foundations of the System of Radiological Protection. ICRP Publication 138. Ann.
ICRP 47(1).
ICRP, 2018b. Occupational radiological protection in interventional procedures. ICRP Publication 139.
116

DRAFT REPORT FOR CONSULTATION: DO NOT REFERENCE

3719
3720
3721
3722
3723
3724
3725
3726
3727
3728
3729
3730
3731
3732
3733
3734
3735
3736
3737
3738
3739
3740
3741
3742
3743
3744
3745
3746
3747
3748
3749
3750
3751
3752
3753
3754
3755
3756
3757
3758
3759
3760
3761
3762
3763
3764
3765
3766
3767
3768
3769
3770

Ann. ICRP 47(2).
ICRP, 2022. Optimisation of Radiological Protection in Digital Radiology Techniques for Medical
Imaging. (Out for Public consultation).
ICRP, TG117. Radiological Protection in PET and PET/CT. (under review)https://icrp.org/icrp_group.asp?id=183.
ICRPaedia, 2022. Availavle at http://icrpaedia.org/Main_Page. (last accessed August 2022).
ICRU, 2005 Patient Dosimetry for X-Rays Used in Medical Imaging, ICRU Rep. 74 Bethesda, MD.
ICRU, 2011 Fundamental Quantities and Units for Ionizing Radiation (ICRU Report 85a-Revised).
Bethesda, MD.
ICRU, 2012. Radiation dose and image-quality assessment in computed tomography. ICRU Report 87.
J. ICRU 1, 1–164, Bethesda, MD.
IEC, 2008. Medical electrical equipment – Exposure index of digital X-ray imaging systems – Part
1:Definitions and requirements for general radiography. IEC 62494-1, ed 1.0. , International
Electrotechnical Commission, Geneva.
IEC, 2019 Medical electrical equipment - Part 2-43: Particular requirements for the basic safety andessential performance of X-ray equipment for interventional procedures. 60601-243:2010+AMD1:2017+AMD2:2019 CSV Consolidated version. International ElectrotechnicalCommission, Geneva.
IEC, 2020. Medical electrical eq–ipment - Part 2-43: Particular requirements for the basic safety andessential performance of X-ray equipment for interventional procedures. EN60601-243:2010/A2:2020(AMENDMENT).
Image Gently, 2022. Image Gently. The Image Gently Alliance. Available athttps://www.imagegently.org (last accessed 25 January 2022).
Image Gently, 2022a. Digital Radiography. The Image Gently Alliance. Available athttps://www.imagegently.org/Procedures/Digital-Radiography (last accessed 25 January 2022).
Image Gently 2022b. Fluoroscopy module. The Image Gently Alliance. Available athttps://www.imagegently.org/Procedures/Fluoroscopy/Pause-and-Pulse-Resources (last accessed 25
January 2022).
Image Gently, 2022c. Step lightly Checklist. The Image Gently Alliance. Available athttps://www.imagegently.org/Portals/6/Procedures/ImGen_StpLight_Chcklst.pdf (last accessed 25
January 2022).
Image Gently, 2022d. CT module. https://www.imagegently.org/Procedures/Computed-Tomography ,(last accessed 25 January 2022).
Image Gently, 2022e. Frequently asked questions – Fluoroscopy – Parents. The Image Gently Alliance.
Avalaible at https://www.imagegently.org/Roles-What-can-I-do/Parent/Fluoroscopy (last accessed
22 Jan 2022).
Image Wisely, 2022. Imaging Modalities and Educational Tools. American College of Radiology,
Reston, VA. Available at https://www.imagewisely.org (last accessed August 2022).
Image Wisely, 2022a. Radiation safety cases. American College of Radiology, Reston, VA. Available athttps://www.imagewisely.org/Educational-Tools/Radiation-Safety-Cases (last accessed 25 Jan2022).
Image Wisely, 2022b. CT Protocol Design. American College of Radiology, Reston, VA. Available athttps://www.imagewisely.org/Imaging-Modalities/Computed-Tomography/Protocol-Design (lastaccessed August 2022).
Imanishi, Y., Fukui, A., Niimi, H.,et al., 2005. Radiation-induced temporary hair loss as a radiation
damage only occurring in patients who had the combination of MDCT and DSA. Eur. Radiol. 15,
41–46.
Inkinen, S.I., Mäkelä, T., Kaasalainen, T., Peltonen, J., Kangasniemi, M., Kortesniemi, M., 2022.
Automatic head computed tomography image noise quantification with deep learning. Phys. Med.
99,102–112.
IPEM, 2005. Recommended standards for the routine performance testing of diagnostic x-ray imaging
systems. Report 91. The Institute of Physics and Engineering in Medicine, York.

117

DRAFT REPORT FOR CONSULTATION: DO NOT REFERENCE

3771
3772
3773
3774
3775
3776
3777
3778
3779
3780
3781
3782
3783
3784
3785
3786
3787
3788
3789
3790
3791
3792
3793
3794
3795
3796
3797
3798
3799
3800
3801
3802
3803
3804
3805
3806
3807
3808
3809
3810
3811
3812
3813
3814
3815
3816
3817
3818
3819
3820
3821
3822
3823

IPEM, 2010. Measurement of the Performance Characteristics of Diagnostic X-Ray Systems. Digital
Imaging Systems. IPEM Report 32, Part VII. The Institute of Physics and Engineering in Medicine,York.
Itatani, R., Oda, S., Utsunomiya, D., et al., 2013. Reduction in radiation and contrast medium dose via
optimization of low-kilovoltage CT protocols using a hybrid iterative reconstruction algorithm at
256-slice body CT: phantom study and clinical correlation. Clin. Radiol. 68, e128–e135.
Jamil, A., Mohd, M.I., Zain, N.M., 2018. The consistency of exposure indicator values in digitalradiography systems. Radiat. Prot. Dosim. 182(4), 413–418.
Jaschke, W., Bartal, G., Martin, C.J., Vano, E., 2020. Unintended and Accidental Exposures, Significant
Dose Events and Trigger Levels in Interventional Radiology. Cardiovasc. Intervent. Radiol. 43(8),1114–1121.
Jaschke, W., Schmuth, M., Trianni, A., Bartal, G., 2017. Radiation-Induced Skin Injuries to Patients:
What the Interventional Radiologist Needs to Know. Cardiovasc. Intervent. Radiol. 40(8), 1131–
1140.
Johnson, P.B., Borrego, D., Balter, S., Johnson, K., Siragusa, D., Bolch, W.E., 2011. Skin dose mapping
for fluoroscopically guided interventions. Med. Phys. 38(10), 5490–5499.
Johnson, T.R.C., Krauß, B., Sedlmair, M., et al., 2007. Material differentiation by dual energy CT: initial
experience. Eur. Radiol. 17(6), 1510–1517.
Jones, A.K., Pasciak, A.S., 2011. Calculating the peak skin dose resulting from fluoroscopically guided
interventions. Part I: Methods. J. Appl. Clin. Med. Phys. 12(4),3670.
Jones, A.K., Pasciak, A.S., 2012. Calculating the peak skin dose resulting from fluoroscopically-guided
interventions. Part II: case studies. J. Appl. Clin. Med. Phys. 13(1), 3693.
Jones AK, Balter S, Rauch P, Wagner LK., 2014. Medical imaging using ionizing radiation:
optimization of dose and image quality in fluoroscopy. Med. Phys. 41(1), 014301.
Jones, A.K., Heintz, P., Geiser, W., et al., 2015. Ongoing quality control in digital radiography: Reportof AAPM Imaging Physics Committee Task Group 151. Med. Phys. 42, 6658–6670.
Kaasalainen, T., Mäkelä, T., Kortesniemi, M., 2019. The effect of vertical centering and scout direction
on automatic tube voltage selection in chest CT: a preliminary phantom study on two different CT
equipments. Eur. J. Radiol. Open 6, 24–32.
Kalender, W.A., Koldit,z D., Steiding, C., et al., 2017. Technical feasibility proof for high-resolution
low-dose photon-counting CT of the breast. Eur. Radiol. 27 (3), 1081–1086.
Kalra, M., Maher, M., Toth, T., et al., 2004. Techniques and applications of automatic tube current
modulation for CT. Radiology 233, 649–657.
Kanal, K.M., Butler, P.F, Sengupta, D., Bhargavan-Chatfield, M., Coombs, L.P., Morin, R.L., 2017. U.S.
diagnostic reference levels and achievable doses for 10 adult CT examinations. Radiology 284, 120–
133.
Kanal, K.M., Butler P.F., Chatfield, M.B. et al., 2022. U.S. Diagnostic Reference Levels and Achievable
Doses for 10 Pediatric CT Examinations. Radiology. 302(1), 164–174.
Kim, Y. K., Sung, Y. M., Choi, J. H., Kim, E.Y., Kim, H.S., 2013. Reduced radiation exposure of thefemale breast during low-dose chest CT using organ-based tube current modulation and a bismuth
shield: comparison of image quality and radiation dose. Am. J. Roentgenol. 200(3), 537–544.
Ko, S.M., Kim, T.H., Chun, E.J., Kim, J.Y., Hwang, S.H. 2019. Assessment of Left Ventricular
Myocardial Diseases with Cardiac Computed Tomography. Korean J. Radiol. 20(3), 333–351.
Kleinman, P., Strauss, K., Zurakowski, D., Buckley, K.S., Taylor, G.A., 2010. Patient Size Measured
on CT Images as a Function of Age at a Tertiary Children’s Hospital. Am. J. Roentgenol. 194, 1611–
1619.
Kotiaho, A., Manninen, A-L., Nikkinen, J., Nieminen, M.T., 2018. Comparison of organ-based tube
current modulation and bismuth shielding in chest CT. Rad. Prot. Dosim 185. 42–48.
Kwan, M.L., Miglioretti D.L., Marlow E.C., et al., 2019. Trends in Medical Imaging During Pregnancy
in the United States and Ontario, Canada, 1996 to 2016. JAMA Netw. Open 3;2(7), e197249.
Lambert, J.W., Gould, R.G., 2016. Evaluation of a net dose-reducing organ-based tube current
modulation technique: comparison with standard dose and bismuthshielded acquisitions. Am. J.
Roentgenol. 206(6), 1233–1240.
118

DRAFT REPORT FOR CONSULTATION: DO NOT REFERENCE

3824
3825
3826
3827
3828
3829
3830
3831
3832
3833
3834
3835
3836
3837
3838
3839
3840
3841
3842
3843
3844
3845
3846
3847
3848
3849
3850
3851
3852
3853
3854
3855
3856
3857
3858
3859
3860
3861
3862
3863
3864
3865
3866
3867
3868
3869
3870
3871
3872
3873
3874
3875
3876

Lazarus, E., Debenedectis, C., North, D., et al., 2009. Utilization of imaging in pregnant patients: 10year review of 5270 examinations in 3285 patients 1997-2006. Radiology 251, 517–524.
Lee, C., Lodwick, D., Hurtado, J., Pafundi. D., Williams, J.L., Bolch, W.E., 2010. The UF family ofreference hybrid phantoms for computational radiation dosimetry. Phys. Med. Biol. 55(2), 339–363.
Lee, C., Goo, J., Ye, H., Ye, S., Park, C., Chun, E. Im, J., 2008. Radiation dose modulation techniquesin the multidetector CT era: from basics to practice. Radiographics 28 ,1451–1459.
Leipsic, J., Nguyen G., Brown J., Sin, D., Mayo, J.R., 2010. A prospective evaluation of dose reduction
and image quality in chest CT using adaptive statistical iterative reconstruction. Am. J. Roentgenol.
195, 1095–1099.
Lell, M.M., Kachelrieß, M., 2020. Recent and Upcoming Technological Developments in Computed
Tomography. Investigative Radiology 55(1), 8–19.
Leung, A.N., Bull, T.M., Jaeschke, R., et al., 2012. American Thoracic Society documents: an official
American Thoracic Society/Society of Thoracic Radiology Clinical Practice Guideline—Evaluationof Suspected Pulmonary Embolism in Pregnancy. Radiology 262, 635–646.
Lin, P.J.P., Goode, A.R., Corwin, F.D. et al., 2022. AAPM Task Group Report 272: Comprehensive
acceptance testing and evaluation of fluoroscopy imaging systems. Med. Phys. 49(4), e1–e49.
Mahesh, M., 2001. Fluoroscopy: Patient Radiation Exposure Issues. Radiographics 21(4), 1033–1045.
Mahesh, M., 2016. What is the CT dose check standard, and why do CT scanners need to be incompliance?. J. Am. Coll. Radiol. 13, 64–66.
Mahesh, M., Hevezi, J.M., 2010. Features to Consider When Selecting a New CT Scanner. J. Am. Coll.
Radiol. 7(10), 820–822.
Malchair, F., Dabin, J., Deleu, M., Maccia, C., Merce, M.S., 2018. Standards for digital dose reporting,D 9.141 VERIDIC project, European Joint Programme for the Integration of Radiation Protection
Research EJP-CONCERT, H2020 – 662287.
Malik, R.F., Buljac-Samardžić, M., Akdemir, N., Hilders, C., Scheele, F., 2020. What do we reallyassess with organisational culture tools in healthcare?. An interpretive systematic umbrella review
of tools in healthcare. BMJ Open Qual. 9(1), e000826.
Marsh, R.M., Silosky, M., 2019. Patient Shielding in Diagnostic Imaging: Discontinuing a Legacy
Practice. Am. J. Roentgenol. 212(4), 755–757.
Martin, C.J., 2007. The importance of radiation quality for optimisation in radiology. Biomed Imaging
Interv J 3(2), e38.
Martin, C.J., Huda, W., 2013. Intercomparison of patient CTDI surveys in three countries. Radiat. Prot.
Dosim. 153, 431–440.
Martin, C.J., Sookpeng, S., 2016. Setting up computed tomography automatic tube current modulation
systems. J. Radiol. Prot. 36, R74–R95.
Martin, C.J., Vassileva, J., Vano, E., et al. 2017. Unintended and accidental medical radiation exposuresin radiology: guidelines on investigation and prevention. J. Radiol. Prot. 37, 883–906.
Martin, C.J., Harrison, J.D., Rehani, M.M., 2020. Effective dose from radiation exposure in medicine:past, present, and future. Phys. Med. 79, 87–92.
Matsubara, K., Koshida, K., Ichikawa, K., et al., 2009. Misoperation of CT automatic tube current
modulation systems with inappropriate patient centring: phantom studies. Am. J. Roentgenol. 129,
862–865.
Matsunaga, Y., Chida, K., Kondo, Y., et al., 2019. Diagnostic reference levels and achievable doses forcommon computed tomography examinations: Results from the Japanese nationwide dose survey.
Br. J. Radiol. 91, 20180290.
Maués, N.H.P.B, Alves, A.F.F., Pavan. A.L.M., et al., 2018. Abdomen-pelvis computed tomography
protocol optimization: an image quality and dose assessment. Radiat. Prot. Dosim. 184(1), 66–72.
Mayer, C., Meyer, M. Fink, C., et al., 2014. Potential for radiation dose savings in abdominal and chest
CT using automatic tube voltage selection in combination with automatic tube current modulation.
Am. J. Roentgenol. 203, 292–299.
Mayo-Smith, W.W., Hara, A.K., Mahesh, M., Sahani, D.V., Pavlicek, W., 2014. How I do it: Managing
radiation dose in CT. Radioloyg 273(3), 657–672.
McCabe, B.P., Speidel, M.A., Pike, T.L., Van Lysel, M.S., 2011. Calibration of GafChromic XR-RV3
119

DRAFT REPORT FOR CONSULTATION: DO NOT REFERENCE

3877
3878
3879
3880
3881
3882
3883
3884
3885
3886
3887
3888
3889
3890
3891
3892
3893
3894
3895
3896
3897
3898
3899
3900
3901
3902
3903
3904
3905
3906
3907
3908
3909
3910
3911
3912
3913
3914
3915
3916
3917
3918
3919
3920
3921
3922
3923
3924
3925
3926
3927
3928
3929

radiochromic film for skin dose measurement using standardized x-ray spectra and a commercial
flatbed scanner. Med. Phys. 38(4), 1919–1930.
McCollough, C.H., Zink, F.E., Kofler, J. M., et al., 2002. Dose optimisation in CT: Creation,
implementation and clinical acceptance of size-based technique charts. Radiology 225, 591.
McCollough, C.H., Bruesewitz, M,R., Kofler, J.M., 2006. CT dose reduction and dose management
tools: overview of available options. Radiographics 26, 503–512.
McCollough, C.H., Schueler, B.A., Atwell, T.D., et al., 2007. Radiation exposure and pregnancy: whenshould we be concerned?. Radiographics. 27(4), 909–918.
McCollough, C.H, Leng, S., Yu, L., Fletcher, J.G., 2015. Dual- and Multi-Energy CT: Principles,Technical Approaches, and Clinical Applications. Radiology 276, 637–653.
McCollough, C.H., Boedeker, K., Cody, D. et al. 2020. Principles and applications of multienergy CT:
Report of AAPM Task Group 291. Med. Phys. 47(7), e881.
McCullough, C.H., Leng, S. 2019. Use of artificial intelligence in computed tomography dose
optimisation. Ann. ICRP. 49, S1, 113–125.
McFadden, S., Roding, T., de Vries, G., et al., 2018. Digital imaging and radiographic practise indiagnostic radiography: An overview of current knowledge and practice in Europe. Radiography24(2), 137–141.
McKenney, S.E., Seibert, J.A., Lamba, R., Boone, J.M., 2014. Methods for CT automatic exposure
control protocol translation between scanner platforms. J. Am. Coll. Radiol. 11, 285–291.
Mello-Amoedo, C.D., Martins, A.N., Tachibana, A., Pinho, D.F., Baroni, R.H., 2018. Comparison ofradiation dose and image quality of abdominopelvic CT using iterative (AIDR 3D) and conventional
reconstructions. Am. J. Roentgenol. 210, 127–133.
Mentrup, D., Neitzel, U., Jocke, S., Maack, H-I., Menser, B., 2014. Grid-like contrast enhancement forbedside chest radiographs acquired without anti-scatter grid.
Philips SkyFlow, 1-8. Available athttps://www.documents.philips.com/assets/20170523/16bb7fdd54a24d369a89a77c015ccedd.pdf (lastaccessed 11 Dec 2021).
Merzan, D., Nowik, P., Poludniowski, G., Bujila R., 2017. Evaluating the impact of scan settings on
automatic tube current modulation in CT using a novel phantom. Br. J. Radiol. 90(1069), 20160308.
Mettler, F.A, Thomadsen, B.R, Bhargavan, M., et al., 2008. Medical radiation exposure in the US in
2006: preliminary results. Health Phys. 95, 502–7.
Mohammadinejad, P., Mileto, A., Yu, L. et al., 2021. CT Noise-Reduction Methods for Lower-Dose
Scanning: Strengths and Weaknesses of Iterative Reconstruction Algorithms and New Techniques.
Radiographics, 41(5), 1493–1508.
Montalescot, G., Sechtem, U., Achenbach, S., Andreotti. F., Arden C., Budaj. A., 2013. ESC guidelines
on the management of stable coronary artery disease: the Task Force on the Management of Stable
Coronary Artery Disease of the European Society of Cardiology. Eur Heart J. 2013;34, 2949–3003.
Morimoto, L.N., Kamaya, A., Boulay-Coletta, I., et al., 2017. Reduced dose CT with model-based
iterative reconstruction compared to standard dose CT of the chest, abdomen, and pelvis in oncology
patients: intra-individual comparison study on image quality and lesion conspicuity. Abdom. Radiol.
42, 2279–2288.
Morrison, G., John, S.D., Goske, M.J., et al., 2011. Pediatric digital radiography education for radiologic
technologists: current state. Pediatr. Radiol. 41, 602–610.
Mortensen, K.H., Tann, O., 2018. Computed tomography in paediatric heart disease. Br. J. Radiol 91,
20180201.
Mulkens, T.H, Bellinck, P., Baeyaert, M., et al., 2005. Use of an automated exposure control mechanism
for dose optimization in multi-detector row CT examinations: clinical evaluation. Radiology 237,
213–223.
Nagayama, Y., Sakabe, D., Goto, M. 2021. Deep Learning–based Reconstruction for Lower-Dose
Pediatric CT: Technical Principles, Image Characteristics, and Clinical Implementations.
Radiographics 41, 1936–1953.
NCRP, 2010. Radiation Dose Management for Fluoroscopically-guided Interventional Medical
Procedures, NCRP Rep. 168, National Council on Radiation Protection and Measurements,
120

DRAFT REPORT FOR CONSULTATION: DO NOT REFERENCE

3930
3931
3932
3933
3934
3935
3936
3937
3938
3939
3940
3941
3942
3943
3944
3945
3946
3947
3948
3949
3950
3951
3952
3953
3954
3955
3956
3957
3958
3959
3960
3961
3962
3963
3964
3965
3966
3967
3968
3969
3970
3971
3972
3973
3974
3975
3976
3977
3978
3979
3980
3981
3982

Bethesda, MD.
NCRP, 2019. Medical Exposure of Patients in the United States. NCRP Report No 184, National
Council on Radiation Protection and Measurements, Bethesda, MD.
NCRP, 2021. NCRP Recommendations for Ending Routine Gonadal Shielding During Abdominal and
Pelvic Radiography. NCRP Statement No 13, National Council on Radiation Protection andMeasurements, Bethesda, MD.
Neil, S., Padgham, C., Martin, C.J., 2010. A study of the relationship between peak skin dose andcumulative air kerma in interventional neuroradiology and cardiology. J. Radiol. Prot. 30(4), 659–
672.
NEMA, 2013. Standard Attributes on CT Equipment Related to Dose Optimization and Management.
XR 29-2013. National Electrical Manufacturers Association, Rosslyn, VA. Available athttps://nema.org/Standards/Pages/Standard-Attributes-on-CT-Equipment-Relatedto-DoseOptimization-and-Management.aspx#download (last accessed April 2017).
NEMA, 2016. NEMA Standards Publication XR 31-2016. Standard Attributes on X-ray Equipment forInterventional Procedures (2016). National Electrical Manufacturers Association, Rosslyn, VA.
NEMA, 2018. NEMA Standards Publication XR 27-2013 (R2018) X-ray Equipment for Interventional
Procedures User Quality Control Mode. National Electrical Manufacturers Association, Rosslyn, VA.
Nikupaavo, U., Kaasalainen, T., Reijonen, V., 2015. Lens dose in routine head CT: comparison ofdifferent optimization methods with anthropomorphic phantoms. Am. J. Roentgenol. 204(1), 117–
123.
Ota, J., Yokota, H., Takishima, H., et al., 2019. Breast exposure reduction using organ-effective
modulation on chest CT in Asian women. Radiology 119, 108651.
Pasquino, M., Cutaia, C., Poli, M., et al., 2018. Patient's Peak Skin Dose evaluation using Gafchromic
films in interventional cardiology procedures and its correlation with other dose indicators. Phys.
Med. 53, 103–107.
Persson, M., Bujila, R., Nowik, P., et al., 2016. Upper limits of the photon fluence rate on CT detectors:
Case study on a commercial scanner. Med. Phys. 43 (7), 4398–4411.
Prakash, P., Kalra, M.K., Kambadakone, A., et al., 2010. Reducing Abdominal CT Radiation Dose With
Adaptive Statistical Iterative Reconstruction Technique. Invest. Radiol. 45, 202–210.
Qu, M., Jaramillo-Alvarez, G., Ramirez-Giraldo, J.C., et al., 2013. Urinary stone differentiation inpatients with large body size using dualenergy dual-source computed tomography. Eur. Radiol. 23(5),1408–1414.
Queiroz, P.M., Santaella, G.M., de Castro Lopes, S.L.P., Haiter-Neto, F., Freitas, D.Q., 2020.
Characteristics of radiographic images acquired with CdTe, CCD and CMOS detectors in skull
radiography. Imaging Sci. Dent. 50(4), 339–346.
Radvany, M.G., Mahesh, M. 2015., Last Series Hold: A Feature on Fluoroscopy Systems With the
Potential to Reduce Patient and Operator Dose. J. Am. Coll. Radiol. 12(8), 860–861.
Rajendran, K., Petersilka, M., Henning, A. et al. 2021a. Full field-of-view, high-resolution, photoncounting detector CT: technical assessment and initial patient experience. Phys. Med. Biol. 66,
205019.
Rajendran, K., Petersilka, M., Henning, A. et al. 2021b. First Clinical Photon-counting Detector CT
System: Technical Evaluation. Radiology 303(1), 130–138.
Rajagopal, J.R., Farhadi, F., Richards, T., et al., 2021. Evaluation of Coronary Plaques and Stents with
Conventional and Photon-counting CT: Benefits of High-Resolution Photon-counting CT. Radio.l
Cardiothoracic Imaging 3(5), e210102.
Rampado, O., Marchisio, F., Izzo, A., et al., 2009. Effective dose and image quality evaluations of an
automatic CT tube current modulation system with an anthropomorphic phantom. Eur. J. Radiol. 72,
181–187.
Ranallo, F., 2013. CT protocol optimization over the range of CT scanners: Recommendations andmisconceptions. http://amos3.aapm.org/abstracts/pdf/77-22652-312436-91821.pdf, (last accessed
4 August 2022).
Ranallo, F.N., Szczykutowicz, T., 2015. The Correct Selection of Pitch for Optimal CT Scanning:
Avoiding Common Misconceptions. J. Am. Coll. Radiol. 12, 423–424.
121

DRAFT REPORT FOR CONSULTATION: DO NOT REFERENCE

3983
3984
3985
3986
3987
3988
3989
3990
3991
3992
3993
3994
3995
3996
3997
3998
3999
4000
4001
4002
4003
4004
4005
4006
4007
4008
4009
4010
4011
4012
4013
4014
4015
4016
4017
4018
4019
4020
4021
4022
4023
4024
4025
4026
4027
4028
4029
4030
4031
4032
4033
4034
4035

Rana, V. K., Rudin, S., Bednarek, D.R., 2016. A tracking system to calculate patient skin dose in realtime during neurointerventional procedures using a biplane x-ray imaging system. Med. Phys. 43,
5131–5144.
Ranschaert, E.R., Morozo,v S., Algra, P.R., 2019. Artificial intelligence in medical imaging:
Opportunities, applications and risks. Springer Nature Switzerland, Cham.
RCR, 2014. Standards of practice of computed tomography coronary angiography in adult patients.
Royal College of Radiologists, London. Available at http://www.rcr.ac.uk/ (last accessed August2022).
Rehani, M.M., Vassileva, J., 2018. Survey of imaging technology and patient dose recording indeveloping countries. Radiat. Prot. Dosim. 181(3), 240–245.
Rizzo, S., Kalra, M., Schmidt, B., et al., 2006. Comparison of angular and combined automatic tube
current modulation techniques with constant tube current CT of the abdomen and pelvis. Am. J.
Roentgenol. 186, 673–679.
Roehrig, H., Krupinski, EA., Hulett, R.. 1997. Reduction of patient exposure in pediatric radiology.
Acad. Radiol. 4, 547–557.
Rostad, B.S., Applegate, K.E., Kim, T., Mansour, R.M., Milla, S.S., 2018. Multiphase acquisitions inpediatric abdominal-pelvic CT are a common practice and contribute to unnecessary radiation dose.
Pediatr. Radiol. Nov 48(12), 1714–1723.
Ruzsics, B., Gebregziabher, M., Lee, H., et al., 2009. Coronary CT angiography: automatic cardiacphase selection for image reconstruction. Eur. Radiol. 19(8), 1906–1913.
Ryckx, N., Sans-Merce, M., Schmidt, S., et al., 2018. The use of out-of-plane high Z patient shielding
for fetal dose reduction in computed tomography: Literature review and comparison with MonteCarlo calculations of an alternative optimisation technique. Phys. Med. 48, 156–161.
Sahiner, B., Pezeshk, A., Hadjiiski, L.M., Wang, X., Drukker, K., Kenny H. Cha, K.H. et al., 2019. Deeplearning in medical imaging and radiation therapy. Med. Phys. 46 (1), e1–e36.
Saltybaeva, N., Platon, A., Poletti, P.-A., Hinzpeter, R., Merce, M.S., Alkadhi, H., 2020. Radiation Doseto the Fetus From Computed Tomography of Pregnant Patients—Development and Validation of a
Web-Based Tool. Invest. Radiol., 55, 762–768.
Samara, E., Stratakis, J., Enele Melono, J.M., Mouzas, I.A., Perisinakis, K., Damilakis, J., 2009.
Therapeutic ERCP and pregnancy: is the radiation risk for the embryo trivial?. Gastrointest. Endosc.
69, 824–831.
Samei, E., Dobbins III, J.T., Lo, J.Y., Tornai, M.P., 2005. A framework for optimising the radiographic
technique in digital X-ray imaging. Radiat. Prot. Dosim. 114, 220–229.
Samei, E., Kruipinski, E., 2018. The handbook of medical image perception and techniques. editors.
2nd ed. Cambridge University Press, New York.
Samei, E., Järvinen, H., Kortesniemi, M., et al., 2018. Medical imaging dose optimisation from groundup: expert opinion of an international summit. J. Radiol. Prot. 38(3), 967–989.
Schenzle, J.C., Sommer, W.H., Neumaier, K., et al., 2010. Dual Energy CT of the Chest: How About
the Dose?. Invest. Radiol. 45(6), 347–353.
Schindera, S.T., Odedra, D., Raza, S.A., et al., 2013. Iterative Reconstruction Algorithm for CT: Can
Radiation Dose Be Decreased While Low-Contrast Detectability Is Preserved?. Radiology 269(2),511–518.
Schmidt, B., Saltybaeva, N., Kolditz, D., Kalender, W.A. 2013. Assessment of patient dose from CT
localizer radiographs. Med. Phys.40(8), 084301.
Schulz, B., Kuehling, K., Kromen, W., et al., 2012. Automatic bone removal technique in whole-bodydual-energy CT angiography: performance and image quality. Am. J. Roentgenol. 199(5), W646–
W650.
Seeram, E., 2019. Digital Radiography Physical Principles and Quality Control, second edition.
Springer Nature Singapore Pte Ltd., Singapore.
Shahir, K., McCrea, J.M., Lozano, L.A.S., Goodman, L.R. 2015. Reduced z-axis technique for CT
Pulmonary angiography in pregnancy--validation for practical use and dose reduction. Emerg.
Radiol. 22(6), 651–656.
Shields, E., Bushong, S.C., 2012. Beware the Mask. J. Am. Coll. Radiol. 10(2), 149–152.
122

DRAFT REPORT FOR CONSULTATION: DO NOT REFERENCE

4036
4037
4038
4039
4040
4041
4042
4043
4044
4045
4046
4047
4048
4049
4050
4051
4052
4053
4054
4055
4056
4057
4058
4059
4060
4061
4062
4063
4064
4065
4066
4067
4068
4069
4070
4071
4072
4073
4074
4075
4076
4077
4078
4079
4080
4081
4082
4083
4084
4085
4086
4087
4088

Shrimpton, P.C., Hillier, M.C., Meeson, S., Golding, S.J., 2014. Doses from computed tomography (CT)examinations in the UK—2011 review PHE-CRCE-013. Public Health England, Chilton.
Singh, R., Wu, W., Wang, G., et al., 2020. Artificial intelligence in image reconstruction: The change ishere. Phys. Med. 79, 113–125.
Smith-Bindman, R., Wang, Y., Chu, P. et al., 2019. International variation in radiation dose for computed
tomography examinations: prospective cohort study. BMJ 364, k4931.
Siegel, M.J., Ramirez-Giraldo, J.C., 2019. Dual-Energy CT in Children: Imaging Algorithms andClinical Applications. Radiology 291, 286–297.
Söderberg, M., 2016 Overview, practical tips and potential pitfalls of using automatic exposure control
in CT: Siemens Care Dose 4D. Radiat. Prot. Dosim. 169, 84–91.
Söderberg, M., Gunnarsson, M., 2010. Automatic exposure control in computed tomography—anevaluation of systems from different manufacturers. Acta. Radiol. 51, 625–34.
Sodickson, A.D., Keraliya, A., Czakowski, B., Primak, A., Wortman, J., Uyeda, J.W. 2021. Dual energy
CT in clinical routine: how it works and how it adds value. Emerg. Radiol. 28(1), 103–117.
Solomou, G., Papadakis, A.E., Damilakis, J., 2015. Abdominal CT during pregnancy: A phantom study
on the effect of patient centring on conceptus radiation dose and image quality. Eur. Radiol. 25, 911–
921.
Solomou, G., Perisinakis, K., Tsetis, D., Stratakis, J., Damilakis, J., 2016. Data and methods to estimate
fetal dose from fluoroscopically guided prophylactic hypogastric artery balloon occlusion. Med.
Phys. 43, 2990–2997.
Sookpeng, S., Martin, C.J., Cheebsumon, P., Pengpan, T., 2017. Practical experiences in the transfer ofclinical protocols between CT scanners with different ATCM systems. J. Radiol. Prot. 37, 84–96.
Sookpeng, S., Martin, C.J., Gentle D.J., 2013. Comparison of different phantom designs for CT scannerautomatic tube current modulation system tests. J. Radiol. Prot. 33, 735–761.
Sookpeng, S., Martin, C.J., Gentle, D.J., 2015. Investigation of the influence of image reconstruction
filter and scan parameters on operation of automatic tube current modulation systems for different
CT scanners. Radiat. Prot. Dosim. 163, 521–30.
Sookpeng, S., Martin, C.J., Gentle, D.J., Lopez-Gonzalez, M.R., 2014. Relationships between patientsize, dose and image noise under automatic tube current modulation systems. J. Radiol. Prot. 34,
103–123.
Sookpeng, S., Martin, C. J., Krisanachinda, A. 2020. Design and use of a phantom for testing andcomparing the performance of computed tomography automatic tube current modulation systems. J.
Radiol. Prot. 40, 753–773.
SPR 2008. Practice Quality Improvement Module for Performance of the Voiding Cystourethrogram.
The
Societyfor
Pediatric
Radiology,
Reston,VA.
Availableathttps://www.pedrad.org/Portals/5/Education/PQI/PQI-VCUG%20Template.pdf, (last accessed 24
January 2022).
Stecker, M.S., Balter, S., Towbin, R.B., et al., 2009. SIR Safety and Health Committee; CIRSE
Standards of Practice Committee. Guidelines for patient radiation dose management. J. Vasc. Interv.
Radiol. 20(7 Suppl), S263–S273.
Stevens, G., 2021. Dynamic X-Ray Imaging Systems Used in Medicine – Quality control in
performance characteristics. (IPEM TG report 32 part 8), IPEM-IOP Series in Physics andEngineering inn Medicine. IOP Publishing, Bristol.
Stratis, A., Kottou, S., Molfetas, M., et al., 2013. The effect of combined tube current modulation systemon dose delivered to patients undergoing thoracic and abdominal CT with a 128-slice scanner. Radiat.
Prot. Dosim. 153, 206–211.
Strauss, K.J., Goske, M.J., Kaste, S.C., et al., 2010. Image Gently: Ten Steps You Can Take to Optimize
Image Quality and Lower CT Dose for Pediatric Patients. Am. J. Roentgenol. 194, 868–873.
Sun, K., Han, R., Zhao, R., et al., 2018. Evaluation of dual energy computed tomography iodine
mapping within the myocardial blood pool for detection of acute myocardial infarction: correlation
with histopathological findings in a porcine model. Br. J. Radiol 91, 20170569.
Supanich, M.P., 2013. Tube current modulation. AAPM 3rd CT Dose summit, Strategies for CT Scan
Parameter
Optimization,
15–16
March
2013, Arizona,
USA.
Available
at123DRAFT REPORT FOR CONSULTATION: DO NOT REFERENCE

4089
4090
4091
4092
4093
4094
4095
4096
4097
4098
4099
4100
4101
4102
4103
4104
4105
4106
4107
4108
4109
4110
4111
4112
4113
4114
4115
4116
4117
4118
4119
4120
4121
4122
4123
4124
4125
4126
4127
4128
4129
4130
4131
4132
4133
4134
4135
4136
4137
4138
4139
4140
4141

www.aapm.org/meetings/2013CTS/documents/Fri_10SupanichTCMFinal.pdf (las accessed 18
January 2016).
Suzuki, K., 2017. Overview of deep learning in medical imaging. Radiol. Phys. Technol. 10(3), 257–
273.
Tabari, A., Gee1, M.S., Singh, R., 2020. Reducing Radiation Dose and Contrast Medium Volume With
Application of Dual-Energy CT in Children and Young Adults. Am. J. Roentgenol. 214, 1199–1205.
Taguchi, N., Oda, S., Nakaura, T., et al., 2018. Contrast enhancement in abdominal computed
tomography: influence of photon energy of different scanners. Br. J. Radiol. 91, 20170285.
Taguchi, K., Iwanczyk, J.S., 2013. Vision 20/20: Single photon counting x-ray detectors in medical
imaging. Medical Physics. 40 (10), 100901.
Talei Franzesi, C.R., Ippolito, D, Riva, L., Fior, D., Cangiotti, C., Sironi, S., 2018. Diagnostic value of
iterative reconstruction algorithm in low kV CT angiography (CTA) with low contrast medium
volume for transcatheter aortic valve implantation (TAVI) planning: image quality and radiation dose
exposure. Br. J. Radiol. 91, 20170802.
Tan, S.K., Yeong, C.H., Raja Aman, R.R.A., et al., 2018. Low tube voltage prospectively ECG-triggered
coronary CT angiography: a systematic review of image quality and radiation dose. Br. J. Radiol.
91, 20170874.
Teeuwisse, W.M., Geleijns, J., Broerse, J.J., Obermann, W.R., van Persijn, van Meerten, E.L., 2001.
Patient and staff dose during CT guided biopsy, drainage and coagulation. Br. J. Radiol. 74, 720–
726.
Tsalafoutas, I.A., Tsapaki, V., Triantopoulou, C., Gorantonaki, A., Papailiou, J., 2007. CT-guided
interventional procedures without CT fluoroscopy assistance: patient effective dose and absorbed
dose considerations. Am. J. Roentgenol. 188, 1479–1484.
Tzedakis, A., Damilakis, J., Perisinakis, K., Stratakis, J., Gourtsoyiannis, N., 2005. The effect of zoverscanning on patient effective dose from multi-detector spiral computed tomography
examinations. Med. Phys. 32, 1621–1629.
Uffmanna, M. Schaefer-Prokopb, C., 2009. Digital radiography: The balance between image quality
and required radiation dose. Eur. J. Radiol. 72, 202–208.
UNSCEAR, 2000. Sources and Effects of Ionizing Radiation. Volume I: Sources. Annex D. Medical
radiation exposures. United Nations Scientific Committee on the Effects of Atomic Radiation,
Vienna.
UNSCEAR, 2008. Sources and Effects of Ionizing Radiation. Volume I: Sources. Annex A. Medical
radiation exposures. United Nations Scientific Committee on the Effects of Atomic Radiation,
Vienna.
UNSCEAR, 2013. Sources and Effects of Ionizing Radiation. Volume II: Annex B - Effects of radiation
exposure of children. United Nations Scientific Committee on the Effects of Atomic Radiation,
Vienna.
UNSCEAR, 2022. Sources, Effects and Risks of Ionizing Radiation. Volume I: Annex A – Evaluationof medical exposure to ionizing radiation United Nations Scientific Committee on the Effects ofAtomic Radiation, Vienna.
Vano, E., Guibelalde, E., Fernandez, J.M., Gonzalez, L., Ten, J.I., 1997. Patiend dosimetry ininterventional radiology using slow films. Br. J. Radiol. 70, 195–200.
Vano, E, Gonzalez, L., Ten, J.I., Fernandez, J.M., Guibelalde, E., Macaya, C., 2001. Skin dose and dosearea product values for interventional cardiology procedures. Br. J. Radiol. 74(877), 48–55.
Vano, E., Fernández, J.M., Ten, J.I., Sanchez, R.M., 2022. Benefits and limitations for the use ofradiation dose management systems in medical imaging. Practical experience in a university hospital.
Br J Radiol. 95, 20211340.
Van Straten, M., Venema, H.W., Majoie, et al. 2007. Image quality of multisection CT of the brain:
thickly collimated sequential scanning versus thinly collimated spiral scanning with image
combining. Am. J. Neurorad. 28(3), 421–427.
Vassileva, J., Rehani, M., Kostova-Lefterova, D. et al. 2015. A study to establish international diagnostic
reference levels for paediatric computed tomography. Radiat. Prot. Dosim. 165(1–4), 70–80.
Vassileva, J., Applegate, K.E., Paulo, G., Vano, E., Holmberg, O.J. 2022. Strengthening radiation
124

DRAFT REPORT FOR CONSULTATION: DO NOT REFERENCE

4142
4143
4144
4145
4146
4147
4148
4149
4150
4151
4152
4153
4154
4155
4156
4157
4158
4159
4160
4161
4162
4163
4164
4165
4166
4167
4168
4169
4170
4171
4172
4173
4174
4175
4176
4177
4178
4179
4180
4181
4182
4183
4184
4185
4186
4187
4188
4189
4190
4191

protection education and training of health professionals: conclusions from an IAEA meeting. J.
Radiol. Prot. 42, 011504.
Walsh, C., Gorman D., Byrne, P., Larkin, A., Dowling, A., Malone, J.F., 2008. Quality assurance ofcomputed and digital radiography systems. Rad. Prot. Dosim. 129(1-3), 271–275.
WFPI, 2022. The World Federation of Pediatric Imaging. Available at https://www.wfpiweb.org/ (lastaccessed Jan 2022).
WHO, 2016. Communicating Radiation Risk in Paediatric Imaging: Information to support healthcare
discussions about benefit and risk. World Health Organization, Geneva.
Available athttps://www.who.int/ionizing_radiation/pub_meet/radiation-risks-paediatric-imaging/en /(lastaccessed July 2020).
Willemink, M.J, de Jong, P.A., Leiner, T., et al., 2013a. Iterative reconstruction techniques for computed
tomography Part 1: Technical principles. Europ. Radiol. 23(6), 1623–1631.
Willemink, M.J., Leiner, T., de Jong, P.A., et al., 2013b. Iterative reconstruction techniques forcomputed tomography part 2: initial results in dose reduction and image quality. Europ. Radiol. 23(6), 1632–1642.
Willis, C.E., Slovis, T.L., 2004. The ALARA concept in pediatric CR and DR: dose reduction inpediatric radiographic exams – A white paper conference Executive Summary. Pediatric Radiology
34, S162–S164.
Wilson, S.M., Prasan, A.M., Virdi, A., et al., 2016. Real-time colour pictorial radiation monitoring
during coronary angiography: effect on patient peak skin and total dose during coronary angiography.
EuroIntervention. 12(8), e939–e947.
Wilson, J.M., Christianson, O.I., Richard, S., Samei, E., 2013. A methodology for image quality
evaluation of advanced CT systems. Med. Phys 40, 031908.
Wilting, J.E., Zwartkruis, A., van Leeuwen, M.S., Timmer, J., Kamphuis, A.G.A., Feldberg M., 2001.
A rational approach to dose reduction in CT: individualized scan protocols. Eur. Radiol. 11, 2627–
2632.
Winklehner, A., Goetti, R., Baumueller, S., et al., 2011. Automated attenuation-based tube potential
selection for thoracoabdominal computed tomography angiography: improved dose effectiveness.
Invest. Radiol. 46, 767–773.
Wood T.J., Moore C.S., Stephens A., Saunderson, J.R., Beavis, A.W., 2015. A practical method tostandardise and optimise the Philips DoseRight 2.0 CT automatic exposure controlsystem. J. Radiol.
Prot. 35, 495–506.
Worrall, M., Vinnicombe, S., Sutton, D., 2020. Determining patient abdomen thickness from a single
digital radiograph with a computational model: clinical results from a proof of concept study. Brit.
J. Radiol. 93, 20200010.
Woussen, S., Lopez-Rendon, X., Vanbeckevoort, D., Bosmans, H., Oyen, R., Zanca, F., 2016. Clinicalindications and radiation doses to the conceptus associated with CT imaging in pregnancy:
aretrospective study. Eur. Radiol. 26, 979–985.
Yeoman, L.J, Howarth, L., Britten, A., et al., 1992. Gantry angulation in brain CT: dosage implications,effect on posterior fossa artifacts, and current international practice. Radiology 184, 113–116.
Zhang D., Ayala R., 2014. Auto couch height positioning compensation—making SURE exposure asmarter dose reduction tool Toshiba America Medical Systems CTWP12271US. Toshiba
Corporation,
Tokyo,pp
1–8.
Available
atwww.toshiba-medical.eu/de/wpcontent/uploads/sites/2/2015/01/Auto-Couch-Height-Positioning-2014-aquilion.pdf (last accessed
18 July 2016).
Zhang, X., Chen, J., Yu, N., et al., 2019. Improving image quality with model-based iterative
reconstruction at quarter of nominal dose in upper abdominal CT. Br. J. Radiol 92, 20180137.
Zhang, L.J., Zhou, C.S., Schoepf, U.J. et al., 2013. Dual-energy CT lung ventilation/perfusion imaging
for diagnosing pulmonary embolism. Eur. Radiol. 23(10), 2666–2675.

125

DRAFT REPORT FOR CONSULTATION: DO NOT REFERENCE

4192

ANNEX A. DOSE QUANTITIES AND UNITS

4193
4194
4195
4196
4197
4198
4199

(A1) Table A.1 lists specific dose quantities and units used to describe radiation exposure indifferent x-ray imaging applications. These are not patient doses that relate directly to risks toindividuals but are indicators in terms of air kerma characterising radiation exposure for the
purposes of QC, comparison of practice, and setting DRLs as a tool for optimisation. The
notation recommended in ICRU, (2005) on patient dosimetry is given based on the fundamental
dose quantities defined in ICRU, (2011). Abbreviations in common use and other terms
sometimes used for the same quantities are also included.

4200
4201

Table A.1. Dose quantities and units currently used in diagnostic radiology, their recommended
notation and other commonly used symbols, together with the field of application.
Dose quantity

Equationnotation(ICRU)

Unit

Abbreviationand othersymbols used

Incident air kerma atpatient entrance
surface
Entrance surface air
kerma

Ka,i

mGy

Ki; IAK

Ka,emGy

Ke; ESAK

Air kerma-area
product

PKA

mGy·cm2
radiography
Gy·cm2(fluoroscopy)

KAP

Incident air kerma at
the patient entrance
reference point**
Computed
tomography air
kerma index
Volume CT air kerma
index

Ka,r

Gy

CAK
(Cumulative
air kerma)

CK

mGy

CTDI, CK

Cvol

mGy

CTDIvol, Cvol

Air kerma-length
product

PKL

mGy.cm

DLP, PKL,CT

Mean glandular
dose**DG

mGy

MGD, AGD

Similarquantities

Field ofapplication
Radiography,
fluoroscopy

Entrancesurface dose(ESD)*
Dose-area
product(DAP)*CT doseindex(CTDI)*
Volume CT
dose index(CTDIvol)Dose-length
product*

Radiography
andfluoroscopy
Radiography,
fluoroscopy,
CBCT
Fluoroscopy
and FGI
proceduresComputed
tomography
Multidetector
computed
tomography
Computed
tomography
Mammography

4202
4203
4204

* Air kerma and dose in air are numerically equal in diagnostic radiology energy range.
**This quantity is not directly measured, but due to the standardised approach for its calculation, it iscommonly displayed on equipment displays

4205

A.1. References

4206
4207
4208
4209

ICRU, 2005. Patient Dosimetry for X-Rays Used in Medical Imaging, ICRU Rep. 74 Bethesda, MD.
ICRU, 2011. Fundamental Quantities and Units for Ionizing Radiation (ICRU Report 85a-Revised).
Bethesda, MD.

126

DRAFT REPORT FOR CONSULTATION: DO NOT REFERENCE

4210
4211

ANNEX B. AUTOMATED SYSTEMS FOR RADIATION EXPOSURE
MONITORING

4212
4213
4214
4215

(B1) As discussed in ICRP (2022), larger scale audits of patient doses can potentially be carriedout if dose data can be downloaded from electronic storage in DICOM headers or PACS/RIS
archives. Dose management systems can be particularly useful for this (Loose et al., 2021). A
brief explanation of some of the systems and standards used is given here.

4216

B.1. Digital Imaging and Communication in Medicine (DICOM)

4217
4218
4219
4220
4221
4222
4223
4224
4225
4226
4227

(B2) DICOM is an international standard for storing and exchanging medical images andimage related information (Boos et al., 2016). The DICOM standard is used in the vast majorityof digital imaging modalities in medicine and is not a file format – rather it is a protocol that isused to capture, transfer, store and display medical data (Pianykh, 2013). Each basic DICOM
component is called an object and contains the relevant data elements or attributes. There areboth image and non-image objects; one example of a non-image object is a Radiation Dose
Structured Report (RDSR) but there are many other derived structured documents. Each itemof equipment that uses the DICOM standard has an associated conformance statement; thisdetails the extent to which the equipment conforms to the standard and provides essential
information regarding interoperability. A plethora of information concerning the DICOM
standard can be found at NEMA (2020).

4228

B.2. Radiation Dose Structured Report (RDSR)

4229
4230
4231
4232
4233
4234
4235
4236
4237
4238
4239
4240
4241
4242
4243
4244
4245
4246
4247
4248
4249
4250
4251
4252
4253

(B3) The RDSR is a DICOM information object that records data from radiation events influoroscopy, CT, mammography, CR and DR procedures in a standard format. A RDSR object
is like an image, with the major difference that it does not contain pixel data; instead, it contains
structured information organised in a hierarchical tree structure (Omar, 2016; AAPM, 2019).
Without such an object, it would be necessary to use entire image sets to access and store
exposure information, with concomitant increases in storage space and transmission
requirements. There would also be some loss of data resulting from technical issues(Sechopoulos et al., 2015).
(B4) A vast amount of information is stored in the RDSR structure, including data that is
general for all irradiation events, such as device serial number and performing physician, andalso data that is specific for each irradiation event, such as tube voltage and beam angle.
(Sechopoulos, 2015; Hellström, 2018). Modality specific parameters such as KAP, DLP, EI,
and AGD (Annex A) are also recorded as required. The RDSR data is available on most CT
scanners manufactured after 2012 (NEMA, 2013) and is available on the newest digitalradiography and interventional systems. RDSR support on equipment used for interventional
radiology was mandated by IEC in 2010 (IEC, 2010) and should be available on all equipment
manufactured subsequently. For example, an entire interventional fluoroscopic sequence
involving one pedal press will be included in the RDSR as a single irradiation event(Sechopoulos, 2015). So, if a particular interventional examination requires the exposure pedal
to be pressed 15 times, 15 individual irradiation events are captured.
(B5) However, there are many attribute fields in the RSDR that are optional rather thanmandatory (NEMA, 2016) and each manufacturer has also taken advantage of the possibility
to adapt the standard with so-called “private fields” (Malchair, 2018). There are consequently
many differences between the structured reports provided by different vendors, which makes
the task of interrogating them even more complex.
127

DRAFT REPORT FOR CONSULTATION: DO NOT REFERENCE

4254
4255
4256
4257
4258
4259
4260
4261
4262
4263
4264

(B6) An RDSR reader is necessary to covert the DICOM object data into a form that is
generally accessible. Radiation dose management systems typically enable RDSR data to beviewed, manipulated, and exported. It should be noted that although most current PACS
solutions support RDSR storage and review, some legacy PACS have limited ability to handle
RDSR data objects (AAPM, 2019). There are open-source solutions, for example OpenRem,
which also has a simple skin dose assessment package (McDonagh, 2014).
(B7) AAPM (2019) recommend that a physicist needs to verify radiation generating
equipment has the capability of generating a correct RDSR as part of the acceptance test, or as
part of a software upgrade for RDSR functionality. Understanding of DICOM and RDSR
should be a requirement for medical physicists involved in optimisation of all radiology
equipment.

4265

B.3. Picture archiving and communication system (PACS)

4266
4267
4268
4269
4270
4271
4272
4273
4274

(B8) A Picture Archiving and Communication System (PACS) is a medical imaging
technology which provides secure, economical storage for digital medical images, whileallowing convenient access and retrieval for multiple users. Images are stored and transfer
using DICOM format and other data stored in standard formats. A PACS has four major
components: the imaging modalities, a secured network for transmission of the patient images
and data, workstations for the review and interpretation of images, and archives for storage andretrieval of images and reports. Medical documentation and images can be securely stored in
off-site servers and accessed safely from sites in different locations via workstations or mobile
devices.

4275

B.4. Radiology information system (RIS)

4276
4277
4278
4279
4280

(B9) A Radiology Information System (RIS) is a networked software system for managing
medical images and the associated data. It is used for tracking requests for radiology imaging,charges, and other associated information. It can be used in conjunction with PACS and for the
management of archives of images and associated records. Methods are required forclassification and coding of medical procedures for the future development of RISs.

4281

B.5. The RadLex Playbook

4282
4283
4284
4285
4286
4287
4288
4289
4290
4291
4292
4293
4294
4295
4296

(B10) Downloading exposure data for large numbers of patient examinations using automatedsystems will facilitate provision and analysis of dose information. However, one problem
discussed in Section 4 of ICRP (2022) is the lack of a standard nomenclature for imaging
procedures. There may be many variations in names for the same examination used by different
departments even within one organisation. The RadLex Playbook has been created in order tostart a process to address this problem in the USA. It provides a set of names for classificationof examination protocols to enable a standardised approach to coding and identification forentering procedure data into recording systems such as PACS and RIS, and is being encouragedby the ACR (RSNA, 2020). More extensive and unified coding is evolving and the Radlex
Playbook and LOINC radiology codes have now been merged (LOINC, 2022).
(B11) The names and codes are designed to replace or complement old inherited, often
institution-based names to facilitate the tracking of records for imaging procedures to facilitate
requesting, reporting and archiving of electronic medical records. The Playbook describes
imaging examinations as radiology “orderables,” that a referring medical practitioner can enter
into the system. The orderables may be more general than the specific protocol required to128

DRAFT REPORT FOR CONSULTATION: DO NOT REFERENCE

4297
4298
4299
4300
4301
4302
4303
4304
4305
4306

answer the specific clinical question. For example, a “CT abdomen/pelvis with contrast” maybe ordered, and a “CT abdomen/pelvis with contrast, liver protocol” examination performed.
(B12) The RadLex Playbook is aiming to aid the development of a standardised system forcoding to facilitate radiation dose comparisons between institutions. Therefore, organisations
that use it are expected to map their protocol names to the Playbook. This represents a firststage in the implementation of new procedure names that will need collaboration between
clinical staff in different institutions that are aware of local needs and practices and staff of thevendors who know the system capabilities. There is a long way to go before standardisation isachieved and progress will be reliant upon the mapping being performed conscientiously andconsistently by staff across all institutions.

4307

B.6. References

4308
4309
4310
4311
4312
4313
4314
4315
4316
4317
4318
4319
4320
4321
4322
4323
4324
4325
4326
4327
4328
4329
4330
4331
4332
4333
4334
4335
4336
4337
4338
4339
4340
4341
4342
4343
4344
4345
4346

AAPM, 2019. Estimating Patient Organ Dose with Computed Tomography: A Review of Present
Methodology and Required DICOM Information. AAPM Report No.246. American Association of
Physicists in Medicine, New York.
Boos J, Meineke A, Rubbert C, et al., 2016. Cloud-based CT dose monitoring using the DICOMstructured report: fully automated analysis in regard to national diagnostic reference levels. Rofo.
188(3), 288–94.
Hellström, M. 2018. Estimating patient peak skin dose with fluoroscopic procedures. Phys. Med. 52(Suppl.1), 105.
IEC, 2010. Medical Electrical Equipment—part 2-43: Particular Requirements for the Safety of X-Ray
Equipment for Interventional Procedures. IEC 60601-2-43:2010, International ElectrotechnicalCommission, Geneva.
LOINC, 2022. LOINC/RSNA Radiology Playbook User Guide. Regenstrief Institute, Indianapolis, IN.
Available at https://loinc.org/kb/users-guide/loinc-rsna-radiology-playbook-user-guide/, (lastaccessed August 2022).

Loose, R.W., Vano, E., Mildenberger, P., Tsapaki, V., Caramella, D., Sjöberg, J. et al., 2021.
Radiation dose management systems—requirements and recommendations for users fromthe ESR EuroSafe Imaging initiative. Eur Radiol 31, 2106–2114.
Malchair, F., Dabin, J., Deleu, M., Maccia, C., Merce, M.S., 2018. Standards for digital dose reporting,D 9.141 VERIDIC project, European Joint Programme for the Integration of Radiation Protection
Research. H2020–662287, EJP-CONCERT.
McDonagh, E. 2014. OpenRem. Free and Open Source Radiation Exposure Monitoring for the physicist.
The Royal Marsden NHS Foundation Trust, London.
NEMA, 2013. Standard Attributes on CT Equipment Related to Dose Optimization and Management.
XR 29-2013. National Electrical Manufacturers Association, Washington, DC.
NEMA, 2016. Standard Attributes on X-ray Equipment for Interventional Procedures (2016). XR 312016. National Electrical Manufacturers Association, Washington, DC.
NEMA, 2020. The DICOM Standard 2020c. , National Electrical Manufacturers Association,
Washington, DC.
Omar, A., Bujila, R., Fransson, A. et al., 2016. A framework for organ dose estimation in x-ray
angiography and interventional radiology based on dose-related data in DICOM structured reports.
Phys Med Biol 61(8), 3063–3083.
Pianykh, O., 2013 Digital Imaging and Communications in Medicine (DICOM) - A Practical
Introduction and Survival Guide. Springer Berlin, Heidelberg.
RSNA, 2020. RadLex radiology lexicon. Radiological Society of North America, Oakbrook, Il.
Available at: https://www.rsna.org/en/practice-tools/data-tools-and-standards/radlex-radiologylexicon, (last accessed August 2022).
Sechopoulos, I., Trianni, A., Peck, D., 2015. The DICOM Radiation Dose Structured Report: What It
Is and What It Is Not. J Am Coll Radiol 12(7), 712–713.

129

DRAFT REPORT FOR CONSULTATION: DO NOT REFERENCEABBREVIATIONS

4347
4348

AAMC

American Association of Medical Colleges

4349

AAPM

American Association of Physicists in Medicine

4350

ABC

Automatic brightness control (see ADRC)

4351

ACGME

Accreditation Council for Graduate Medical Education.(US)

4352

ACR

American College of Radiology

4353

ACR-SPR

ACR with Society of Paediatric Radiology

4354

ACR-STRACR with Society of Thoracic Radiology

4355

ADRC

Automatic dose rate control (also known as ABC)

4356

AEC

Automatic exposure control

4357

AFC

Alternative Forced Choice

4358

AGD

Average Glandular Dose

4359

AI

Artificial intelligence

4360

ALARA

As low as reasonably achievable

4361

AP

Antero-posterior

4362

ATCM

Automatic tube current modulation

4363

ATVS

Automatic voltage selection

4364

BIR

British Institute of Radiology

4365

BMD

Bone mineral density

4366

CAK

Cumulative air kerma at patient entrance reference point

4367

CBCT

Cone beam computed tomography

4368

CoDE

Conceptus Dose Estimation

4369

CR

Computed radiography

4370

CNR

Contrast-to-noise ratio

4371

COMARE

Committee On Medical Aspects od Radiation in the Environment (UK)

4372

CT

Computed tomography

4373

CTA

Computed tomography angiography

4374

CTCA

Computed tomography coronary angiography

4375

CTDI

Computed tomography dose index

4376

CTDIvol

Volume averaged CTDI

4377

CTPA

CT pulmonary angiography

4378

DAP

Dose-area product (see KAP)

4379

DDR

Direct digital radiography (radiation sensitive diodes)

4380

DI

Deviation index
130

DRAFT REPORT FOR CONSULTATION: DO NOT REFERENCE

4381

DICOM

Digital Imaging and Communications in Medicine

4382

DL

Deep Learning

4383

DLIR

Deep Learning based Image Reconstruction

4384

DLP

Dose Length Product

4385

DMS

Dose management system

4386

DR

Digital radiography - diode array storage

4387

DRL

Diagnostic reference level

4388

DSA

Digital subtraction angiography

4389

DVT

Deep Venous Thrombosis

4390

DECT

Dual Energy Computed Tomography

4391

DXA

Dual x-ray absorptiometry

4392

EC

European Commission

4393

ECG

Electrocardiogram

4394

EFOMP

European Federation of Medical Physics

4395

EI

Exposure index

4396

EIT

Target exposure index

4397
4398

EMR

Electronic Medical Record (individual health information relating to imaging
request)

4399

ESAK

Entrance surface air kerma. (also Ka,e)

4400

ESD

Entrance surface dose (see ESAK)

4401

ESR

European Society of Radiology

4402

ESTRO

European Society for Therapeutic Radiology and Oncology

4403

EU

European Union

4404

FBP

Filtered back projection

4405

FDA

Food and Drug Administration (US Federal Agency)

4406

FGI

Fluoroscopically guided intervention

4407

FP

Flat panel

4408

GI

Gastro-intestinal

4409

GU

Genitourinary

4410

HU

Hounsfield unit

4411

HVL

Half-value layer

4412

IAEA

International Atomic Energy Agency

4413

IAK

Incident air kerma (at image receptor or patient entrance surface)

4414

ICRU

International Commission on Radiation Units and Measurement

4415

IDR

Indirect digital radiography (phosphor and diode)131

DRAFT REPORT FOR CONSULTATION: DO NOT REFERENCE

4416

IEC

International Electrotechnical Commission

4417

IED

Integrated Energy Detector

4418

II

Image intensifier

4419

IOP

Institute of Physics (UK)

4420

IPEM

Institute of Physics and Engineering in Medicine (UK)

4421

IR

Iterative reconstruction

4422

ISO

International Standards Organisation

4423

KAP

Kerma-area product (also PKA) (ICRP Glossary - Air-kerma, product)

4424

KSC

Knowledge, skills and competences

4425

kV

kilovoltage

4426

LIH

Last image hold

4427

LUT

Look up table

4428

LOINC

Logical Observation Identifiers Names and Codes

4429

mAs

Milliamp seconds (tube current x exposure time)

4430

MC

Monte Carlo

4431

MCU

Micturating cystourethrogram

4432

MGD

Mean Glandular Dose

4433

ML

Machine learning

4434

MPR

Multi-planar reformats

4435

MOSFET

Metal oxide semiconductor field effect transistor

4436

MRI

Magnetic resonance imaging

4437

NCRP

National Council on Radiation Protection and Measurement (US)

4438

NEMA

National Electrical Manufacturers Association (US)

4439

NICU

Neo-natal intensive care unit

4440

PA

Postero-anterior

4441

PACS

Picture archiving and communication system

4442

PCCT

Photon counting CT

4443

PiDRLsPaediatric Diagnostic Reference Levels

4444

PET

Positron emission tomography

4445

PHE

Public Health England

4446

PICC

Peripheral insert of central catheter

4447

PMMA

Polymethyl methacrylate

4448

pps

pulses per second

4449

PSD

Peak skin dose132

DRAFT REPORT FOR CONSULTATION: DO NOT REFERENCE

4450

QA

Quality Assurance

4451

QC

Quality Control

4452

QMS

Quality Management System

4453

RANZCR

Royal Australia and New Zealand College of Radiologists

4454

RDSR

Radiation dose structured report

4455

R/F

Radiography / Fluoroscopy

4456

RIS

Radiology information system

4457

RP

Radiological protection

4458

RPOP

Radiation protection of patients (IAEA)

4459

RSNA

Radiological Society of North America

4460

SAFRAD

SAFety in RADiological procedures (IAEA)

4461

SID

Source to image receptor distance

4462

SIIM

Society for Imaging Informatics in Medicine

4463

SNR

Signal to noise ratio

4464

SPECT

Single photon emission tomography

4465

SPR

Scan projection radiograph

4466

SPR

Society for Paediatric Radiology (US)

4467

SSD

Source to skin distance

4468

SSDE

Size specific dose estimate

4469

UNSCEAR

United Nations Scientific Committee on the Effects of Atomic Radiation

4470

UQCM

User quality control manual

4471

US

Ultrasound

4472

VCUG

Voiding cystourethrography

4473

VMI

Virtual Monoenergetic Images (CT)

4474

WHO

World Health Organisation

4475

WL

Window level

4476

WW

Window width

4477

2D, 3D, 4D

2-, 3- or 4- dimensional

133

DRAFT REPORT FOR CONSULTATION: DO NOT REFERENCE

4478

GLOSSARY

4479
4480

Only terms not included in the ICRP main Glossary are included here. The ICRP Glossary canbe viewed at the website address: http://icrpaedia.org/ICRP_Glossary.

4481

Artificial intelligence (AI)

4482
4483
4484
4485
4486
4487
4488
4489
4490
4491
4492
4493
4494
4495
4496
4497
4498
4499
4500
4501
4502
4503
4504
4505
4506
4507
4508
4509
4510
4511
4512
4513
4514

Artificial intelligence (AI) can be characterised as a collection of algorithms
performing tasks that give a machine the capability to imitate human intelligence. AI
is becoming important in medical imaging, as lesions and organs appearing in medical
images are too complex to be described by a simple equation or a hand-crafted model
as used in conventional computer aided diagnostics. AI methodology has there are subdomains: machine learning (ML) and deep learning (DL) that are used to create
decisions based on analysis of large-scale training data sets.
Automatic dose rate control (ADRC)
Device that automatically determines the exposure rate needed to provide an image of
selected image quality during fluoroscopy by sampling the x-ray intensity transmitted
through the patient at the image receptor. The changes in exposure are achieved throughadjustment of the tube potential (kV) and tube current (mA) according to predetermined
relationships.
Automatic tube current modulation (ATCM)
ATCM or automatic exposure control (AEC) determines the tube current level in CT
required to maintain the level of image quality or image noise selected by the operator
throughout a scan. The adjustments are based on the scan projection radiographrecorded before the main scan.
Contrast-to-noise ratio (CNR)
CNR is the contrast divided by the noise. Contrast means the difference between pixel
values of any two regions in the image. Noise means the graininess of the image which
is typically described by a single value representing the standard deviation of pixel
values within a (homogeneous) region in the image. Note: This quantity needs to be
introduced because attention only to the ‘contrast’ has often resulted in images ofhigher quality than needed for confident diagnosis. Noise is also a measure of image
quality. Images having higher noise levels do not necessarily undermine diagnostic
accuracy; rather, the contrast-to noise ratio may be similar or improved.
Deep learning (DL)Deep learning is a subset of machine learning developed to learn from data without
being explicitly programmed. In DL the data are fed through several data processing
layers in a neural network architecture, providing higher abstraction level features fromthe original input data. As with machine learning, DL methods require to be trainedusing datasets containing large numbers of appropriate images and has become feasible
134

DRAFT REPORT FOR CONSULTATION: DO NOT REFERENCE

4515
4516
4517
4518
4519
4520
4521
4522
4523
4524
4525
4526
4527
4528
4529
4530
4531
4532
4533
4534
4535

due to the enormous number of medical images now being produced. DL methods areyielding promising results in medical imaging related to diagnostic tasks, such as lesion
or tissue localisation, segmentation, classification and prediction of clinical outcomes.
DL image reconstruction (DLIR) is being used for CT.
DICOM-Digital Imaging and Communications in Medicine
Digital imaging standard describing a set of protocols describing how radiology images
are identified in a structured way, formatted and communicated. DICOM ismanufacturer-independent and was developed by the American College of Radiology
and the National Electronic Manufacturers Association. Provision of an agreed
structured format facilitates the exchange of files between devices that have thecapability of accepting image and patient data in DICOM format. DICOM 3.0 is thecurrent version. http://medical.nema.org/
Dose management system (DMS)
A dose management system comprises software that can store information on patient
dose quantities that is designed to aid the imaging team in optimisation of radiologicalprotection. Tasks performed by such a system might include collecting dosimetric data
to establish local DRLs, checking compliance with DRLs, and provision of data at thetime imaging is being performed to aid optimisation, especially for CT andinterventional procedures. DMSs can also assist in the prevention, detection andreporting of unintended exposures. Other terms such as 'radiation exposure monitoring’and ‘radiation dose monitoring’ are used to describe DMSs.

4536

Entrance surface air kerma (ESAK, Ka,e), see Air kerma, entrance surface in ICRP Glossary.

4537

Flat panel detector

4538
4539
4540
4541
4542
4543
4544
4545
4546
4547
4548
4549
4550

Image sensor used in solid state digital radiography devices containing an array ofsemi-conductor elements similar in principle to the image sensors used in digital
photography. They are used in both projection radiography and as an alternative to xray image intensifiers in fluoroscopy equipment.
Iterative reconstruction
CT image reconstruction technique which typically applies repeated iterative loops offorward projection (producing simulated projection raw data) and back-projection(creating image from projections). Thus, the image reconstruction happens by several
iteration cycles where the iterated image gradually approaches the final image result
converging either by CT image pixel values or by the difference between the simulated
and true (measured) raw data projections. Iterative methods may apply different levelsof physical modelling of the CT scan where increased modelling may enable higher
image quality while also adding to the computational complexity and calculation time.

4551

Kerma-area product (KAP, PKA), see Air-kerma, product in ICRP Glossary

4552

Machine learning (ML)135

DRAFT REPORT FOR CONSULTATION: DO NOT REFERENCE

4553
4554
4555
4556
4557
4558
4559
4560
4561
4562
4563
4564
4565
4566
4567
4568
4569
4570
4571
4572
4573
4574
4575
4576
4577
4578
4579
4580
4581
4582
4583
4584
4585
4586
4587
4588
4589
4590

Machine learning involves the development of computer programmes that can findcomplex patterns, which might represent lesions or other features, within complex data
sets. ML has been developed to learn from data without being explicitly programmed.
In medical imaging, a model or mathematical algorithm is trained on image data sets
to enable it to predict an outcome for new patient data similar to that given by a humanexpert. ML predicts outcomes from new data based on earlier training on large scale.
See also deep learning.
Noise
Noise means the graininess of the image which is typically described by a single value
representing the standard deviation (SD) of pixel values within a (homogeneous) region
in the image. Noise can also be described by a noise-power-spectrum (NPS) which
describes the spatial frequency distribution of the noise. This can also be described as
the grain size distribution of the image noise, or noise texture. Therefore, NPS is morecomprehensive description of the noise compared to single value noise determinedfrom pixel standard deviation.
Patient radiation exposure monitoring
Components, mechanisms, and operational processes related to recording, collecting,and analysing patient radiation exposure data associated with clinical imaging
operation. Here monitoring refers to capturing and meaningfully evaluating patientradiation exposure data and not the actions for quality improvement, an ultimate goal
undertaken by managing patient radiation exposure data.
Radiation Dose Structured Report
Part of the DICOM standard defining the set of DICOM objects providing the radiationdose related parameters by hierarchical description of the irradiation event (e.g. within
entire CT examination or pulsed fluoroscopy image series).
Radiology information system (RIS)
A system that supports the information processing and business requirements ofradiology departments and freestanding image centres.
Reference air kerma (Ka,r)The air kerma at a point in space located at a ﬁxed distance from the focal spot (see“Patient entrance reference point” in ICRPaedia Glossary) accumulated from a whole
x-ray procedure expressed in Gy. The International Electrotechnical Commission (IEC
2010) refers to this quantity as ‘reference air kerma’, while the US Food and Drug
Administration uses the term ‘cumulative air kerma’ (CAK). The International
Commission on Radiation Units and Measurements (ICRU) has not deﬁned a symbol
for this quantity. Ka,r is the notation introduced by the National Council on Radiation
Protection and Measurements (NCRP) in Report No. 168 (NCRP 2010). In many
medical publications the acronym used for this quantity is CAK. This quantity is136

DRAFT REPORT FOR CONSULTATION: DO NOT REFERENCE

4591
4592
4593
4594
4595
4596
4597
4598
4599
4600
4601
4602
4603
4604
4605
4606
4607
4608
4609
4610
4611
4612
4613
4614

referred to in older medical publications as ‘cumulative dose’ and has also been called‘air kerma at the patient entrance reference point’ and ‘reference point air kerma’.
Scan projection radiograph (SPR)
Radiographic image produced on a CT scanner by moving the couch through the CT
gantry with the x-ray tube in a fixed position. Scan projection radiographs are
performed at the start of a CT examination and are used for selecting the region of the
body to be scanned and providing a measure of attenuation along the body foradjustment of tube current in automatic tube current modulation. A variety of terms areused for the SPR by different vendors: namely scout view, topogram, surview, andscanogram.
Signal to noise ratio (SNR)
Signal-to-noise ratio (abbreviated SNR or S/N) is a measure that compares the level ofa desired signal to the level of background noise. Closely related to CNR but instead ofcontrast as in CNR the signal is involved in SNR.
Spatial frequency
Any signal can be composed of a series of harmonic (sine and cosine) waves. An image
can be interpreted as a composition of an infinite number of periodic sine and cosine
waves. A short wavelength (equivalent to high spatial frequency) corresponds withsmall detail, whereas a long wavelength (equivalent to low spatial frequency)
corresponds with large objects in the image. The relationship between spatial frequency
and detail size is inversely proportional. In order to avoid confusion with the term time
frequency, spatial frequency is used. A common unit is line pairs per millimetre (lp mm1).

137

DRAFT REPORT FOR CONSULTATION: DO NOT REFERENCE

4615

ACKNOWLEDGEMENTS

4616
4617
4618
4619
4620

This is the second report from Task Group 108 on Optimisation of digital radiography,
fluoroscopy, and computed tomography in Medical Imaging established by the Commission
in 2018, led by members of ICRP Committee 3. The first report set out general guidance on
optimisation methods in digital radiology covering the general principles of optimisation, while
this report deals with practical application for radiography, fluoroscopy and CT.

4621
4622
4623
4624

ICRP thanks all those involved in the development of this publication for their hard work anddedication, and members of Committee 3, and Claire Cousins and Eliseo Vañó, emeritus
members of the Main Commission, for helpful review and discussion about the content of the
publication.

4625
4626

Task Group 108 members (2018–present)
C J Martin (Chair)
K Applegate
J Damilakis
I.Hernandez-Giron

D Husseiny
M Kortesniemi
H Khoury
KH Ng

M Perez
D G Sutton
J Vassileva

4627
4628

Committee 3 Critical Reviewers

4629

M. Mahesh

4630

Main Commission Critical reviewers

4631

K-W. Cho

4632

Editorial members

4633
4634
4635
4636
4637

C.H. Clement (Scientific Secretary and Annals of the ICRP Editor-in-Chief)
T. Yasumune (Assistant Scientific Secretary and Annals of the ICRP Associate Editor)(2022–)
H. Yu (Assistant Scientific Secretary and Annals of the ICRP Associate Editor)(2022–)

4638

Committee 3 during the preparation of this report4639(2017–2021)
K Applegate (Chair)C J Martin (Vice-Chair)
M Rehani (Secretary)
J Alsuwaidi
M Bourguignon
M-C Cantone

4640

Makoto Hosono
M. KaiS Demeter

M Hosono
K Kang
R LooseJ Marti-Clement
Y Niu

C RuebeW. SmallD. G Sutton
L Van Bladel(2021–present)
K Applegate (Chair)C J Martin (Vice-Chair)
D. G Sutton (Secretary)
M-C Cantone
J Damilakis
M Hosono

A Isambert
M Kortesniemi
M Mahesh
J Marti-Clement
J C Paeng
C Ruebe138

W. SmallÅ Søvik
I Thierry-Chef
I Williams
W ZhuoDRAFT REPORT FOR CONSULTATION: DO NOT REFERENCE

4641
4642
4643

Committee 3 emeritus members

4644

Main Commission members at the time of approval of this publication

4645
4646
4647
4648
4649
4650
4651
4652
4653
4654
4655

Chair: W. Rühm, Germany
Vice-Chair: D.A. Cool, USA
Scientific Secretary: C.H. Clement, Canada; sci.sec@icrp.org*

4656
4657

*

S. Mattsson

K.E. Applegate, USA
F. Bochud, Switzerland
S. Bouffler, UK
K.W. Cho, Korea
G. Hirth, Australia
M. Kai, Japan
D. Laurier, France

M.M. Rehani

M. Rosenstein

S. Liu, China
S. Romanov, Russia
T. Schneider, France
A. Wojcik, Sweden

Emeritus members
R.H. Clarke, UK
F.A. Mettler Jr, USA
R.J. Pentreath, UK
R.J. Preston, USA
C. Streffer, Germany
E. Vañó, Spain

Although formally not a Main Commission member since 1988, the Scientific Secretary is an
integral part of the Main Commission.

4658

139